I think you might be confusing a few things a little:

1. A PNR does not have to have the same surname!! You can have 50 different surnames in one PNR and it wouldn't be any different from if it was all the same surname.

2. 2 different PNRs cannot be combined into one PNR locator. What they usually do is to make a note that the two different PNRs are travelling together. (but still, having one PNR is a lot more effective).

The only way to "combine" two PNRs is to cancel both PNRs and make a new one with 2 names.

Can't answer you re. the maiden/current name problem though...