I usually leave my plants tied all the way through because i am lazy. I just make sure there is some slack round the branch so it can grow.
Yes your right about the new growth comming from the nodes and I usually move leaves about so the new growth can get more light.
I have read you shouldn't really smoke round your plants but it has never stopped me.
As for temps I work in C but 16-18c I think is the coldest you can go without stunting your plant to much but I may be wrong. The cold does bring out any purple colour in your plants during flowering.