Testimony IS evidence. TP's sworn word will carry a lot of weight with the court absent impeachment of his credibility which I don't think will be found. His story is very credible, imo, and the reasoning for the separate agreement is very sound. Of course he would insist on a separate agreement even if the text was substantially the same.
As has already been suggested, it is not up to TP to prove that he did not sign the filed document. JB has been challenged in court to produce the original. If he cannot, then that adds to TP's credibility. The absence of an original identical to the document filed is evidence, so to speak. IF, just for the sake of discussion, JB does produce something that he claims is the original and it appears to be the same as what was filed, then the burden will shift back to TP/LDB to show TP didn't sign it or that it's an altered doc. Otherwise, it's a he said/he said but JB would have an original doc to back up his word, kwim?
I'm mostly posting here to point out the multi-quote feature to you. It's an unusual feature that WS has and is located near the quote button. It has " marks on it. When you click that button with the " on it, you have copied the text of the post you want to quote but have not opened a reply window. You can click that button on several posts and then click on the quote button when you're ready to reply. I appreciate you taking the time to quote multiple posts to illustrate your points/questions and hope this makes it easier for you to continue doing so.