Max load is whatever you can stuff into the chamber, which is what I understand you were shooting. The gun can stand that on a limited basis, but after some number of shots there will be damage.
However, I think you are asking for the "max load that won't damage the gun over a long period of time", which is a much more difficult question to answer. I don't know of anyone who has attempted to determine that. The damage is gradual, and one would have to set up some sort of subjective criteria for how much would be allowed before calling the test complete. Like any subjective criteria there would be wide variations in what different people would pick for different reasons.
The best answer might be to determine the most accurate load like I described above. I'd feel very comfortable shooting several hundreds, if not thousands, of rounds with that load without worring about damaging the gun. Frankly, I can't imagine why anyone would shoot anything else in a brass framed gun. If you just want a lot of smoke and boom buy a Walker and have at it; a brass frame .36 isn't the gun for that.
By the way, if you really have plastic deformation that gun is unsafe and should be retired.