I don't think they've said but, they seem intent on giving him lots of innings. IMO he'll probably get somewhere around ~140IP in 2013 but, that's just an educated guess.
Yes, they should absolutely stretch him out now that they have started. That being said there will be a time towards the end of the season where Stroman can come up to TO, help the Jays win and get some invaluable experience -- without deviating from the plan.
Stilson has yet to give up a run in AAA, he's looked very good out of the pen. I'm excited to see what he can do going forward. Don't forget Perez will be back at some point after the AS break and Carreno tearing it up as a closer the in AA. Come mid August the Jays should have lots of options to help fill out the BP, also some great depth to deal from in the off-season.
I think the Jays just wanted a LHP, since BAL has struggled against them, for a spot start. I think the nerves got the best of Nolin. I was impressed with his stuff but, his command was all over the place. He'd probably got out of those jams in AA but, MLB hitters will crush mistakes. Hopefully he learned a lesson, goes back to the minors, applies the necessary changes and becomes a better pitcher in the long run.