1) Yes, this is a problem. Your plants are rootbound, more than likely. My rule of thumb on up-potting is once you see roots pushing out of the drainage holes, up-pot immediately.
2) No, that's not the problem.
3) Yes. Believe it or not, defoliation and lollipopping are pretty important. It helps the plant focus on areas you want it to grow, while not having to push energy and nutrients to flarfy bud locations under your canopy.
4) Nah, I doubt it was this. The only ways it could be this is if you picked off potential sugar leaves while the plant is budding, or if you removed potential bud nodes while you defoliated.
5) Yes. You want to give your plant a hardy amount of nitrogen and potassium while it is in veg, along with the proper amount of micro and trace nutrients. My npk is usually around 8-5-8 for feeding in veg. It's at 2-13-10 throughout flowering. Notice, I use hardly any nitrogen during flower. That's because the plant will keep trying to grow bigger and use that nitrogen, instead of building buds and focusing on fattening them up.
I hope this helps.