(Lots of) Home runs are good
You are correct that you want to run a cable to each room from the central switch. In fact, I would run at least 1 more cable than you think you will need to each room, and consider running a line or 2 to other rooms as well - especially if your walls are open. Cable is cheap, and pulling 4 cables instead of 3 is no more work when done at the same time. If you decide later that you want a 4th jack, you either need a small switch (which does limit bandwidth, not really increase latency) or you need to open walls again to pull that 4th cable.
Use a patch panel
Rather than run the cable from the big switch to each room, you should have a patch panel in between. Patch panels basically change the type of connection on the cable (the back is a 110 punch down block, front is an RJ-45 jack), and are a simple pass-through.
This is to ease installation. Pulling cable through walls is best done when the cable is un-terminated. Terminating the cable (i.e., putting the RJ-45 jacks on the end) can and is done, but punching the cable down into a patch panel is so much easier, especially for someone who has never done it before (and it sounds like neither you nor your electrician has). The cost is marginal (again, go bigger than you think you need now), but you save on headaches during installation.
You would then get keystone jacks that allow you to punch down the cable on the other end:
You shove these into wallplates on an electrical box or low-voltage plate:
They make wall-plates with different numbers of openings (usually 1-6), so you can get what you need for each room.
Finally, you would need short (1-2 ft) "patch" cables to connect the patch panel to the big switch. Buy these cables pre-made, as you won't be able to make your own for less. These are typically stranded cable, as it's more flexible.
Your final setup would look something like this:
(the top-most device with jacks is the patch panel, the middle on is the switch, and the bottom would be your router)
Buy solid copper UTP (unshielded twisted pair) cat5e or cat6 cable, rated properly (usually CMR for typical in-wall installation, but you'll need Plenum if you plan to run it in HVAC ducts), and buy multiple boxes if possible. Standard is 1000 ft but smaller lengths are available, and they come in all different colors. A decent-sized house could take 2000-3000 ft of cabling or more, depending on how many runs and where the network closet is. Again, the more boxes you have, the easier installation will be (you typically pull 1 from each box at the same time, so if you want 4 runs to a single location, having 4 boxes is easiest).
If you want things a little cleaner, you can get a wall-mounted mini rack as well:
Just make sure to get one that has the depth and vertical space (measured in "U") you need. They also make ones with hinges that make patch panel installation a bit easier.
Most product images taken from monoprice.com
First step is to get an 802.11ac router. You're probably going to want wireless anyway, so just do that now. Live with that until you decide either you are happy with it, or you need to upgrade. And remember: you won't get ac speeds unless both the router and your device are ac.
If you do need upgrade to wired, buy 2-4 small gigabit switches. Terminate all of the wall plates with cat5e rj45 jacks. At the wall plates with 2 jacks, hook up both jacks to a switch. Since you have daisy-chained drops, the switch will bridge the two halves of the chain. Those cost of doing this should be under $100 for switches and wall plate parts. This is a less than ideal network configuration, but since your bottleneck is going to be your internet connection speed, you will likely hit the limits of performance on this network.
Best Answer
Other than the pesky but unknown question of "exactly which type is it" coaxial cable has not really changed much in 50 years. If it's not defective, it will probably work. Otherwise, it's 50 feet, replace it, or let the provider replace it. Most providers will allow you to try a new service speed and decline if it does not work for you at the claimed speed.
Cable length (new or old) adds to loss of signal strength, and at some point that will affect what service you can get. More expensive, fatter, harder to bend cable can have less loss for the same distance at the same frequency. But it's rarely an issue in normal home-scale cable plants serviced by decent cable-company infrastructure (where they deal with providing enough signal strength to service most of their customers houses without extreme measures being required.) If your current modem permts you to view the signal strength it's getting, you might get some insight - otherwise the cable tech has a fancier meter that will let them know if it can work when they hook it up.
Why you "upgraded" from "perfectly happy to do gigabit" Cat5e to Cat6 for the prospect of possibly having 400 Mbit or even 1 gigabit is beyond me, though.