This may sound like a dumb question. But are you sure that the bolt head itself is spinning, and not the allen key in the hole? I cannot imagine how it could be possible to have *only* the head of the bolt spinning without it becoming detached from the threaded shaft. It seems more likely that the female threads in the converter are stripped & the whole bolt is turning. However in this scenario, I canít imagine that it would hold fluid well enough to allow you to drive it very far. That would account for your leak - however, another thing to know is that the front pump seals are a consistent source of leaks on these transmissions.
If you are planning to use an easy-out and/or rethread the converter, I donít know how you could be absolutely sure to keep *all* the debris out of the converter, which is imperative. Trying to do this may cause you more problems. Although, now that I think about it, you may be able to use a magnet to help localize the shavings, but that is pure speculation, not actual experience speaking. Nothing speaks as strongly as experience. It may just be time to bite the bullet & pull the trans.