A little knowledge is dangerous

Hello to all of the good people of this group. I am requesting your assistance with some questions I have in my basement remodeling. I have just enough knowledge to want to attempt to do this myself. I will type this in sentence fragments to make it a quicker read. Thank you in advance for any advice.
Full basement. Splitting it in half. Some for storage, with the remainder to be a finished entertainment area, 15x15, plus a 5x5 foyer at bottom of stairs. Concrete block walls, concrete floor. This part of the basement has not received any moisture in the 25 years that I've lived here. Very dry, for a basement. Floor newly painted with 2 coats of oil base floor paint. Walls newly painted with one coat of Zissner "dry-lock" type product, and 2 coats of latex.
Plan to erect 2x4 studded, insulated walls. Sheetrock over both walls and ceiling (I know, I know....but don't want to sacrifice height for suspended ceiling...there's not a heck of a lot between the joists in the finished section anyway).
QUESTION 1
This question concerns the studded walls that will be against the exterior basement walls. To leave an air space, and to eliminate a bunch of jogs in the wall, I will not be studding up right against the concrete block. I will be leaving an air space of apx. 8 inches on one wall, and 4 inches on the other. My plan is to stud-up these walls, run electric, insulate with the paper faced insulation, and then sheet rock. I have read about 100 different opinions concerning "vapor barriers", but I don't really know what the established practice is. So, here are some questions. Also note, in high humidity conditions, I will sometimes get condensation against the cold pipes and even the concrete walls. My plan is to insulate the pipes.
Is the above plan sufficient, or should I first put something over the block? I guess I'm concerned about having too many "barriers", where water or condensate cannot evaporate. That is why I just wanted to go with the paper barrier on the insulation batts. Any thoughts? Or, should I go with a non-faced batt insulation between the studs, and cover that with plastic? Or should I go another step and cover the faced batt insulation with plastic, or is this asking for trouble?
QUESTION 2
I've replaced existing switches, hung ceiling fans into existing boxes, etc. However. I've never run new circuits. Bought a good book at Home Depot, and it doesn't seem impossible. Here's my plan on the electric. Me: mount and wire boxes and can lighting, as well as switches. Have electrician inspect, then have him hook into the breaker box. Here's my dumb question....I'm fairly certain that this room will not take any huge appliances, but I'm not 100% sure (I'm not talking washers and dryers....no 240 stuff....but maybe some big TV's etc.). I was thinking of going with 12/2 NM cable. Is this ok, as long as I hook it into a 20 amp breaker? Or, should I go 14/2, with a 15 amp? I was all set to go 12/2, 20 amp, until I read a confusing statement in the book that said something like it is dangerous to hook a 15 amp device to a 20 amp circuit. Can someone clear this up for me? Also, I have plenty of room in my breaker box, and don't mind running 3 or so circuits for this one room. Considering this, in general,how many 15 or 20 amp recepticals are normally placed on one circuit?
QUESTION 3
Any ideas on how to frame out around the basement windows? Materials, techniques, etc?
Sorry for the long post. Any responses are really appreciated.
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Thanks for the input Carpenter Ant. I was considering using green board.
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