Hi Aditya,
I have rudimentary support for titled theorems and end of proof markers working. It also takes care of your bug-report.
That's great news! My fingers are itching to test it ;-)
I have patched core-des so that stopper is also honored when number=no is set.
Does this mean that your patch has already been merged with the official release?
I have a very basic end of proof marker working. Basically, it will handle the marker correctly for proofs that end with paragraphs, and works hard to avoid a page break when the proof ends with a formula or an itemize (in this case, the end of proof marker is in a line of its own). The main macro for putting the proof marker on the right is from Paul Taylor's qed.sty. If you want to test this, I can send you the file offlist. This file is not in a state to be merged into the core right now.
Please send it to me ... Thanks, Oliver