My husband just recently got orders to be an instructor at Tech School. We were rather surprised, since that is normally a duty where you submit a package and have to be selected. However, he didn't apply for it, just got orders for it. It's a 4 year controlled tour. My big question is, he was planning on submitting his packet for OTS in the next year and a half (once he finished his masters), but can he do that while on a controlled tour? Once the tour is over, he will be 3 months away from the age cutoff. And I know that it sometimes takes a few times to get into OTS, esp when your degree isn't technical.
So, will the AF let him out of the special duty if he were to get selected, or would they make him wait to apply until he was done- leaving him the one chance to apply and hope he got in?

Yes. I tought at Kirtland on a code 50. There were two guys I worked with that both got released when they were picked up for OTS. One went to be a Nav, the other a computer dude. No hassles at all. Commanders love it when a sweaty goes to the dark side.