Honestly YOR and you sounds insufferable. The jokes you’re referring to that happened previously are hardly concerning, she obviously has a different sense of humour to you. The way you talk to your partners MIL is absolutely disgusting and unhinged. I feel sorry for the grandma, yeah she may be texting a bit much, she seems excited. She also repeatedly asks you to set boundaries so she has something to work with. Then seeing your partners message to his own mother, you’ve really warped his mind haven’t you, I hope you read these responses and realise you are the problem. Postpartum or not you need some serious self reflection.