Nutes- start at half what the directions say, and work up, watching for burnt looking leaf tips.

Flsuh- No, it can be tap water for the last 1-2 weeks. Just treat it as normal, but with no nutes- water when it needs water, and then about 3 days before harvest, just DRENCH the soil so that water runs out the bottom, let teh plnat use up the rest of that water, and then chop.

Pot size- one gallon per foot of plant height. Sounds like yours is a 3 gallon. You may need to transplant about halfway through flower.

Harvest- Depends on strain. If you see flowers, you are already at week 2. So yes, 6-8 weeks to go is about right.