RE: "My husband and I ..." misuse.
In my opinion, it boils down to it being used as a famous opening to the Queens Speech ages ago. People assume that was the correct usage; after all, the Queen didn't say "My husband and me ..." Absolutely correct, she wouldn't. However, if she'd said "It occurred to my husband and me that ..." this would be correct too.
So, erroneously, folks say 'My husband and I' when they really mean 'my husband and me'.
Isn't it the difference between a collective subject and a collective object?