It's all about Volt Amperes.
NEC 2008 gives us an easy way to do things in residential.
220.82 Dwelling Unit.
(A) Feeder and Service Load. This section applies to a dwelling unit having the total connected load served by a single 120/240-volt
or 208Y/120-volt set of 3-wire service or feeder conductors with an
ampacity of 100 or greater. It shall be permissible to calculate the
feeder and service loads in accordance with this section instead of
the method specified in Part III of this article. The calculated load
shall be the result of adding the loads from 220.82(B) and (C). Feeder
and service-entrance conductors whose calculated load is determined by
this optional calculation shall be permitted to have the neutral load
determined by 220.61.
(B) General Loads. The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder
of the following loads:
(1) 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and
general-use receptacles. The floor area for each floor shall be
calculated from the outside dimensions of the dwelling unit. The
calculated floor area shall not include open porches, garages, or
unused or unfinished spaces not adaptable for future use.
(2) 1500 volt-amperes for each 2-wire, 20-ampere small appliance
branch circuit and each laundry branch circuit covered in 210.11(C)(1)
and (C)(2).
(3) The nameplate rating of the following:
a. All appliances that are fastened in place, permanently connected,
or located to be on a specific circuit
b. Ranges, wall-mounted ovens, counter-mounted cooking units
c. Clothes dryers that are not connected to the laundry branch circuit
specified in item (2) d. Water heaters
(4) The nameplate ampere or kVA rating of all permanently connected
motors not included in item (3).
So we can use 220.82 (B)(2) to figure for the dust collection, freezer, and an additional circuit for receptacles.
1500VA * 3 = 4500VA / 120V = 37.5 Amperes
You'll then have to use the values from the nameplate on the table saw to figure for that (A Volt-Ampere value should be listed on the nameplate, use that number for more accurate calculations). You could also use this method for the dust collection system and freezer since they are both "permanently connected, or located to be on a specific circuit".
3360VA / 240V = 14 Amperes
Now we'll add them up.
37.5A + 14A = 51.5A
So This is what our subpanel will look like.
- 60A double pole breaker in the main panel.
- 6 AWG feeder cable for a run up to 75 ft., 4 AWG feeder cable for a run up to 150 ft.
- 60A main breaker in the subpanel.
- 20A double pole breaker for table saw.
- 20A single pole breaker for dust collector.
- 20A single pole breaker for freezer.
- 20A single pole breaker for convenience receptacles.
Notes:
Don't forget to balance your loads between the two legs in the subpanel.
That is an old "rule of six" panel, which while grandfathered, is illegal under its grandfathering becuse it has 7 main breakers. Going to five is a good plan.
It is a classic "CH" panel which is a very good industrial grade panel, except that the 3/4" breaker width make non-ordinary breakers very expensive (a trait it shares with Square D QO). That makes it perfect for what you plan.
On your subpanel which would be near this panel, I would get a panel with a main breaker, with an eye toward (at some point in the future) cutting it over to be the main panel. In a subpanel, the "main breaker" is nothing more than an on/off switch, it is OK for it to be larger than the feeding breaker.
I would also get a rather large panel, at the very least 42 space and even 60 or 84 if practicable: because panel spaces are dirt cheap and often even come with free breakers, whereas running out of space is painfully expensive.
I would aim for an industrial grade panel of good repute (one available in 3-phase variants, not Homeline, BR, or second tier brands) and avoid the expensive 3/4" breakers (not CH or QO).
Over time, as you find it convenient, i'd migrate all your 1-pole and smaller 2-pole circuits over to the new panel.
For your garage panel anything would do, but I'd go for the same type as your indoor panel, so you can use some of those bonus breakers. Again it's false economy to scrimp on spaces, I'd go 20-30 at least.
Also, since garage spaces need to be on GFCI, consider getting a subpanel which has a "main breaker" which is GFCI, that way all the breakers in that panel would be protected (at the cost of potential nuisance trips, a big deal if you keep a freezer in the garage).
Ed Beal raises some very good concerns about overall capacity. One problem with these "rule of six" panels is there is literally no main breaker to stop you from drawing more than 150A. So it pays to be conservative.
It's a difficult situation because you have two big loads that operate sporadically - the EV charger and the range. And the A/C as a wildcard.
One thing I might suggest, is feed the garage subpanel from the new primary subpanel. And then move everything but the range over to the new subpanel. At that point the only things still in the CH panel would be a 60A range breaker and a 100A subpanel breaker. Even at max, those two could not overload the 150A service (by enough to matter). This would force your entire house (from A/C to EV charger) to share 100A, but would remove the possibility of an overload. This would also save you the $85 you'll spend on a second 100A CH breaker.
Best Answer
Feeder sizing isn't so simple
The minimum rules for service and feeder capacity planning are found in NEC Article 220; while they don't account completely for your usecase, we can use a modified version of those procedures here. We start with the 550sf you gave, and multiply it by 3 to get the lighting and general receptacle load as-if this was part of its parent dwelling unit, giving us 1650VA (volt-amps, similar to watts). We then multiply this by the .35 demand factor for dwelling unit general loads over 3000VA before adding 3000VA to account for the heavy tools circuit and 7500W/VA for the heater as per NEC 220.51. Note that while the demand factor and the heater are both computed as per NEC Article 220 rules, the 3000VA for the tools circuit is an allowance (similar to a pair of Small Appliance Branch Circuits) for the heavy tools circuit due to the unavailability of details about the actual loads found there.
This gives us 11078VA, to which we add the dust collector load. Since we are dealing with a UL listed appliance here, we start with the 20A nameplate amp rating instead of using the tables to look it up, although it doesn't matter in this case anyway since Table 430.248 gives us 20A for the full load current of a 2HP, 115VAC motor. From there, we multiply by 1.25, per NEC 430.24 and 220.50, to get us 25A, which when multiplied by 115VAC gives us 2875VA, for a total load of 13953VA. We then divide this by 240V, giving us a 58A minimum for our feeder ampacity.
While it's possible to wire this using 6AWG THHNs in a conduit or a 6-6-6-6 copper SER cable, that gives us 65A, leaving us little margin for an outbuilding. In NM, we'd have to use 4/3, giving us a 70A feeder instead, but neither NM nor copper SER are cost-effective ways to wire the circuit, at $3.5 to >$4/ft vs the $2.5/ft of materials that using 6AWG THHNs with a 10AWG ground in 3/4" ENT achieves. Nonetheless, we can do better than that by going to aluminum. A 1-1-1-3 aluminum SER cable goes for a mere $1.67/ft or so, and gives us 100A to the shop panel; we can upgrade this to a 1/0-1/0-1/0-2 SER cable to give us a 120A feeder (using a 125A breaker) for just under $2/ft. If that's still too much cost, we can go with a 4-4-4-6 aluminum SER cable for just under $1/ft, but that puts us back at that 65A figure (with a 70A feeder breaker) from the 6AWG THHNs in conduit or 6-6-6-6 copper SER cable mentioned above.
GO BIG OR GO HOME
Now that we've decided on the size of our feeder, we need to figure out what size subpanel to put in, and this is where folks tend to get penny-wise and pound-foolish. You see, ripping out a panel to replace it with a larger one is a big pain in the rear end, and far costlier than what you'd save by using a smaller panel.
Since this is in the same structure, we don't need to worry about a main cutoff (main breaker), nor a second set of ground rods, but we do need a set of separate grounding bars fitted to the panel to land equipment grounding conductors on. Many main lug panels come with these factory fitted, but if yours doesn't, you'll need to buy the correct bars and add them yourself. In either case, you'll want a large panel: a 24-space or 30-space, 125A panel is not at all out of place here, and if you feel like splurging, you can upgrade to a 40-space or 42-space, 200A panel for not that much more. Just make sure that your panel's bonding screw or strap gets pulled out when you install it!
Sidebar: that dust collector may need a bigger breaker
There's one other issue with your setup, and that's your choice of a 20A breaker for the dust collector. You see, motors draw a significant inrush current on startup; for a 2HP, 115VAC, single phase motor, the breaker will have to handle up to 144A for a short period of time. So, there's a decent chance that your 20A breaker will trip on overload when you start the dust collector.
Fortunately, the NEC authors are familiar with this issue, and provide an "out" in 430.52(C), which permits you to size inverse-time (read: regular) breakers protecting a single motor load at up to 250% of the full-load current, or up to 45A for a 20A motor load, provided that the motor has its own overload protection. You probably won't have to go up that high, but having a 25A single-pole breaker for your choice of subpanel handy in case the dust collector won't start on a 20A breaker would be wise (it's the largest value permitted for a 20A motor if the motor doesn't have a built-in overload protector).