Some updates on this, since I last started the thread:
- I called into MP Club and asked for compensation. The agent was nice but very non-committal. She was going to check around and get back to me. I told her very pointedly what I wanted in return for the distress, trauma and time wasted with all the back and forth w/diff parties: I wanted miles.

- I wrote into the DragonAir baggage handling team at the arriving airport. They called me the next day, and offered to repair my bag FOC. However they will NOT cover the cost of any missing items, nor the cost of the damaged TSA lock.

In short, I guess the next step is for me to train my sights on claiming via TSA direct and their contractors (for the cost of the missing item + cost of a missing/presumably cut TSA lock). I downloaded the TSA form and read thru it. Seems very thorough and they require plenty of supporting docs. Oh well, time to get cracking....