I see that you're very angry - I'm sympathetic to that.
When a constellation of misfortunes arrive, it is possible that it's just very bad luck, but commonly it's a result of a complete misinterpretation of the situation: either willful or unconscious. The missing information in your account suggests to me that this is happening here. Landladies are rarely so vindictive without cause; Mahnungs don't arrive without history.
"He did the paperwork in our relationship, which he stole"
You pointedly don't say whether that means he paid the bills for both of you, and now that he's gone you let them go overdue. If it's not the case, why leave it ambiguous?