I hope I am understanding your opening post correctly. I had to read the beginning a couple of times to realize that the person you coincidentally met as a disfellowshipped JW was the same person who is your partner.
Anyway, it sounds like the pioneer comes around for a nice easy hour or more of time when she studies with you. It's all about getting time. I doubt she expects you to ever progress or she would push to come more often. J
W treatment of your partner is due to the disfellowshipping. They are supposed to shun him, not even greet him. Some either are not aware of the situation or are nice to him despite what they are supposed to do. His family overlooks the command to shun because they are family, and probably because nobody in the congregation is aware of their not following rules.
Your mother sounds like a believer in the JW's, but she is also trying to be a good mother and allows her true self to shine through beyond the JW rules. Either way, she doesn't have to shun you and she (along with your partner's parents) can claim "necessary family business" as a reason why they don't shun your partner.
I never figured out what RESP is.
Lastly, grandparents want to be grandparents. Let them spoil the kids a bit and keep straightening it out the best you can. If they want to know what happened to the things they spoiled the kids with, be straight up and say, "They felt that someone else would enjoy that." or whatever the truth is. But I wouldn't want to try to stop/change them on that.