What are the chances I'll be assigned to an airborne unit after jump school with a support MOS?

I would gather better than a 95% chance you'll wind up in the 82nd.

Absolutely impossible to predict.

There is no metric or tracked data for this. It's pure luck.

I would say you have a pretty good chance going to an airborne unit. There are plenty of 5 jump chumps but they are probably gaurd/reserve. Depends on your MOS, availability, slotting, and other things. Good luck AIRBORNE!