Glad you got it taken care of but in the future you can avoid the whole mess by just not removing that mount bracket. The middle rubber insert will normally already be separated from the outer bracket if it's older, but otherwise the 4 'straps' are easily cut and just removing that center insert allows you to pull the old A/C belt off the car and put a new belt on.
I removed my lower left mount (bracket and all) with no issue (just a little surface rust on the bolts) and it is necessary to remove that bracket to install poly bushings, but since many people have you issue you did, I don't think worth the risk in most cases to remove that bracket. (at least not without a liberal application of pb blaster via the drain holes). I personally would have rather left that bracket off than remove material from the frame, but then I don't have access to all the tools you do either
