First, make sure you keep mold under vacuum for an hour or so when you make it, that should get all the bubbles out. Second, 65 PSI is plenty of pressure for resin. Third, tin ot platinum care has nothing to do with mold life; durometer, tear index, elongation index, etc. do. I use either 18 Shore A or 30 Shore A rubbers and have no problems with either. The softer rubber doesn't last for as many casts (20-30 on average) but that's because I use it for parts with severe undercuts. The other rubber (G-1000 by the way) will give 50-60 really good casts before showing significant wear. I do not use release agent with either rubber. The softer one doesn't work well for multipart molds.
So yes, I think you screwed your mold. Call Polymer Tooling Systems in Pennsylvania and get some G-1000 rubber. Keep it under vacuum until all the bubbles are out. Cast at 60-65 PSI and no higher.