bhester,
You've got a lot of good answers for your Q's here - many talented persons in this forum!!!
Maybe this little bit 'o information can help with your last question[s]:
1: As far as circuitry on the 3 wire circuit [basically the home run portion, using the 12/3 NM cable], if you can measure 220 - 240 volts between the black and red wires, then you have setup the homerun circuit OK. That's what you want to have so the grounded conductor [AKA Neutral] does not get overloaded.
In a case where you are using "stacked twins" [4-20 amp 1 pole breakers connected to only two bus poles], then you could connect two seperate 3 wire home runs on the frame, making sure there's 240 volts between the black and red on each home run.
[just threw that in for an FYI
].
2: Glad to see that you are planning to limit the maximum number of outlets per circuit!!
NEC does not limit the number of General Purpose [convenience] type receptacles per circuit on the typical single family dwelling, but that's no reason to follow the "Bare-Bones Minimum" of the NEC! Limiting the number of Receptacles is good design. This is the same on any type of circuit [AKA 2 wire circuit or 3 wire circuit].
For lighting, design the circuit[s] so they will not be overloaded if all lights were on at the same time, plus the largest lamp was used [if medium based screw shell fixtures, rate fixture at no less than 150 va].
3: Be sure to connect the circuits so they work on 1/2 the 3 wire [multiwire] circuit properly. This means keep the grounded conductors' connections uniform throughout their circuitry.
Maybe another member can explain this better!
Basically, the multiwire circuit will be the same as any typical 2 wire circuit, just that the common grounded conductor needs to be spliced and tapped more solidly, plus the need to have the ungrounded conductors connected across both lines - in order to avoid overloading the common grounded conductor [common Neutral].
Please excuse the "Outer Space" explainations! Feel free to comment if needed.
BTW / FYI
to the rest of the group:
BBC America had a Monty Python Marathon all day on the 4th!!! Made sure to record a good 6 hours of it!!!
I'll be using said video tape for refresher course, then attempt to toss a few 1 liners here and there
Scott SET