There's a few ways to do this, though service conductors cannot pass through another building, so all the methods will have to avoid that.
One option would be to install a service disconnect, and then branch from that to the panels.
With this method, you'll handle all the grounding and bonding of the neutral in the disconnect. So you'll install 4 wire feeders from the disconnect to each panel, and keep the neutral isolated in each panel.
Another option is to use the first panel as the service disconnect, and feed the second panel from the first.
With this method, you'll handle all the grounding and bonding of the neutral in the first panel. So you'll feed the second panel with a 4 wire feeder, and isolate the neutral in the second panel.
With is approach, the first panel will have to be rated to handle the total current of both panels.
In all cases, you're going to need properly sized feeders, and a grounding electrode system for each building.
The scope of this project is far too vast for a short answer format site, such as this. I've given a high-level overview of how you might approach the project. For a more detailed plan, please contact a local licensed Electrician.
You may feed a 14-50 outlet directly from your main panel since there are unused breaker slots available. Use the correct breaker of course, and correct conductor type/size for the load. Do not forget voltage drop and temperature ratings when choosing cable.
You do not need to add another sub-panel for a single outlet.
Do not expect the code book to tell you what you can do. It's there to tell you what you can't.
Best Answer
You have to provision 50A for the 10kw heater. We can play some provisioning games on the saw, dust collector, freezer, lights and receps, and allocate them, say, 25-30A. Which puts us at 75-80A.
You could get away with #4Cu / #2Al wire. However, there's very little cost difference just go go all the way to 100A, and that's commonly done.
So, provision 1 AWG aluminum THWN-2 wires with a ground wire of 8 AWG copper bare or 6 AWG Al insulated. There's no reason for a wire size bump at 80'.
This setup would also have the reserve to stick a Tesla charger in there, though Tesla+heater+shop tools simultaneously would be a no-go. Presumably you don't want sawdust on your car :)
1-1/4" conduit should get it done.
Our standard advice is to use a much larger subpanel than you'd ever imagine needing. That's because "buying a subpanel with more spaces" will set you back a couple of Frappucinos, but "having to change your subpanel because you thought too small" is a solid day of work. If the subpanel is attached, even with a breezeway, you don't need a "main breaker" in the subpanel. If detached, you need some kind of shutoff switch, and using a main-breaker panel will only add $20-30 to the cost of the panel. There's no need for the subpanel size to match the feed breaker (100A) size, so feel free to get a 150A-bussed panel with a 125A main breaker if it's on sale :) Also consider "value pack" panels that come with some breakers.