Ride rollers rather than (or in addition to) a trainer during the winter months. It'll really smooth out your spin and make you more confident with your balance. As for paceline riding, there's really no substitute for doing it, but the people you're riding with need to be understanding that you're still working on your skills. I find the best way to learn *any* physical skill is to join a group of people just slightly better than I am. Learn from your pro coach too, so you don't pick up any bad habits from your group.

And +1 on the intervals. And read about training nutrition - I'm sure there's lots on this site and many other places - timing and quantity of protein and carbs are really important when building muscle.