While its certainly not my intention to rain on anyone's parade....and I can absolutely sympathise with everyone's problem here...

I can say that I've never experienced any of these headaches. Mrs. bseller and I do not share the same last name, and I've been able to:
1) upgrade her with no hassles,
2) put her into my PNR if that was needed,
3) take miles out of her MP account fo travel that both of us were going on, and
4) get credit for her on "missing" overseas flights.

I can't address why these things were true, but maybe someone at UA/MP in each case was able to become comfortable that we were in fact married....

Best wishes.