1. No clue sorry. I would have fucked up seeds if I got them on the first 3 plants I grew. (Dead.) So thankfully I used bagseed the first time around. If anything, order the seeds, start the bagseeds, and if everything is going well with the bagseed plants go ahead and plant the other ones.
2. 3x3x8 with only 3 plants. I think you'd be good with a 250W but a 400-600 would be good in case the first grow goes well and you plan on doing more plants the next time around.
3. People seem to like 20-20-20.
4. The vent wont provide enough wind for the plants to be in the gentle breeze they ned to be in so you'll beed a small fan.

Goodluck!!

EDIT: For the odor later in the plant's life, look into making a carbon scrubber.