Sounds like your folding stock is out of whack...I have put tapco folders on several AK builds that I've done, and they have all been able to fire with the stock folded. I wonder what the deal is with yours?? That's not normal. Have you tried calling them up and seeking some sort of resolution... Tapco is very customer service oriented, and will go to lengths to avoid leaving an unhappy customer.
I will concede you a point on the stock, in that where you would get a cheekweld, that area is a little rough.
I have also cut my cheek on a tapco folder, and did the same sandpaper fix you mention.
On the galil handguard, have you tried bending the sides in while you clamp down the handguard ferrule? Some AK's differ a little, and will have varying fits, and ocassionally you will need to do a
custom fit, and either shim up, or remove material.
I suppose I am rather forgiving of tapco products, but I really like a company that's not afraid to try new things, and actually put them at a price point where they're accessable. Not to mention they have real live people who will answer the phone and help you with any issues. Lots of people gripe about the lack of customer service these days, but tapco is one of the few places that actually support the stuff they sell.
Now I just wish they would make a bullpup kit for the AK!