OK:

Great questions.

1) Your builder told you don't shock the pool for 2 weeks. If you do and the walls stain, he'll say you didn't follow his directions.

2) You CAN keep a pool sanitary at FC of 1.5--but that means no stabilizer and you have to check it at least 2 times a day, morning and evening, adding bleach if/when it drops below that. If you can add a third check in the middle of the day, better still. If you see a CC measurement above the minimum (normally 0, but with an FAS-DPD kit you can test to see if the CC is actually <0.5 or really <0.2--in which case you are OK) you'll have to add more chlorine to get rid of it. You cannot let it fluctuate much.

3) I'm not sure what "a bit" means for how long till stabilizer, but if you are going to add ANY (say 10-20ppm) you'll need to maintain FC at 2.0, at least.

4) Ask him about using a small amount of PolyQuat (the only type of algaecide we recommend) to help ensure you don't get an algae bloom. The way I describe it is: look at the various algaecides. If one says "60% Poly...<something, something>..." as the only active ingredient, that's it, regardless of whether they call it Black Algaecide., Mustard Algae Fighter, or whatever.

5) I don't know why you cannot swim when your FC is 1.5 and your CC is 0.