Hey Snap -

Sorry you're having such trouble - tendonitis is the pits. Several years ago I had tendonitis/carpal tunnel in both arms (from computers work), but I learned that one of the important things is to try and keep the hands and wrists in a neutral postition as much as possible. In the 2nd photo you posted, it looks like your wrists are pretty bent (sorry - don't have the anatomical jargon for this!) and that position, especially if the arms are tense, looks like trouble to me.

I am very new to cycling (6 months only) but I have found that using drop bars, and being mostly on the hoods creates a nice neutral position - my thumbs are up, and there's a straight line from my thumbnail along the forearms to the inside of my elbow. Also, sometimes neck and shoulders can interfere with what's happening further down the arm - sounds like you have a PT who can help with this, which is great. The PT I had said that building strength in the arms can really help.

Finally, I have also read what Denise said - that you should be able to lift your arms off the bars, and using your abs, you should be able to maintain that position withour excessive effort (of course, you want to be in a trainer to try this!) - I saw that in this article: How to fit a bike

Good luck - I hope you get it all worked out!