#1 sorry no idea
#2 be careful! yes plug the lights into the timer and the timer into a socket. BUT. you are running a 600w lamp along with fans and anything else, and thats a lot of power into one strip. i recommend keeping the lights and fans seperate so that nothing melts/sparks/burns to the ground.
#3 The begining of a plant's life is an important stage, but cannabis is also a very hardy plant. Erratic lighting would confuse seedlings and possibly slow grow slightly, as this would never happen in nature. However, returning to a consistent (plants like routine) lighting cycle will let them flourish and there will be no significant loss in yield. happy growing
