3 feet is fine. 2 feet is okay. your plants should be fine under that. 5 feet is fine also, but that much distance isn't REQUIRED.
18/6 is a fine schedule, I veg 18/6 on my plants, and they do just fine... not much difference noticeable than with 24/0.
let your buddy do what he wants, prove your thumb is greener by producing better yields, let your buddy be a dick and just stay out of his way... he sounds like the type to blame you if his grow gets fucked up, so just do your own thing and then wait 'til later for the "i told you so"
lol