Hey buddy i can defo see the difference since your first post. There looking better...what lights you using?
I normally feed my plants about a month after i planted them from seed when the nutrients have ran out from my compost. Slowly increasing it will do the trick, they handle alot, ive never managed to overdose my plants with fert.
They can double - triple in size when you put them into flower, depends on many things how big it will get. At a guess id say between 1 - 1.5ft, i normally flower when there around 1ft with about 8 nodes.
Id find out what the infestation is then treat it accordingly, surely what you have done can only help. Im not far off a noob myself never had trouble with bugs