That's a lot of MO activity and it alone could be the culprit—even if it's not from an account that pays Chase. Chase may be snowing you that the closure has anything to do with a Chase account.
That depends on how financially commingled you are with your SO.
how would chase see mo deposits at other banks? even if they filed SARs, chase cant see that as far as I know.
My wife and my finances are pretty separate. she pays accounts with different banks etc. the only thing shared is address. is it worth changing?