This looks like you may have a problem with the BOOTLDR env var in the rommon... Just follow the conversion doc from beginning to end; if you've got a native IOS image on a flashcard you should be OK.
HSRP hello messages come from the real mac on each router, not the virtual one, right? Otherwise, I concur with the previous poster's answer that if different HSRP groups are used with different IP subnets, there shouldn't be a MAC confict.
We're using Q-in-Q for several customers on our MAN, and it works as documented, as does L2PT (tested with CDP and STP, but not VTP as we (and our customers) turn off VTP by default). Astuces: - Only tested both of these technologies with CatOS 7.6 ...