Are you growing Red Robin? How much light do you have? I don't have experience with vermiculite. Some worm castings I've gotten had had very poor drainage, but a kind I got locally that was mixed with a very small portion of peat moss had excellent drainage (usually). The main challenge you'll probably have indoors is getting very much fruit. Your soil will need to have the right nutrients when the plant is in its final pot. Most tomatoes struggle with fruiting in indoor temperatures, too. They tend to like the nights a certain amount cooler than the days.

I'm not a big fan of vermiculite, I read it breaks down and turns into mush. I'd use perlite.