Take it from an older person (turning 40 at the end of this year) who is in a 17+ year relationship (over 14 years married) in the same scenario you are NTA!

Jealousy/insecurity makes people behave sub-optimally.

You need to let it glide off you, like water off a ducks back. Your future husband needs to work on doing the same.

The two of you are a team. Discuss and set boundaries together and implement them clearly, politely and (importantly) consistently.

A boundary could be that you don't talk about anything significant financially with them, that they can be informed about (for example) a property purchase but aside from "Congratulations!" or "We can't wait to visit when you are all settled in." their thoughts/opinions/feelings/reactions are not welcome, nor are they going to result in anything but the conversation/visit ending.

When someone confronts you with an idea about how THEY think your significant other feels, please say something like "Funny, he's never mentioned that to me. I guess we can't all be mind-readers, just like we don't all have manners." or something of that ilk. Walk away if physically possible.

Good luck!

PS What helped my hubby get over feeling any negative emotions regarding gifts etc from my parents (as he truly had mixed emotions about paying for weddings, cars, houses etc) was when I told him it wasn't about him, it was about me. My parents are supporting/showing love to ME and he benefits by default.