I was in your position a few times back when I was younger (41 now).
My advice to you? Tell them to fuck off.
Seriously, I went through it a few times trying to be PIMO with a worldly girlfriend. It isn't worth it. When I say it wasn't worth it, I mean trying to be PIMO. Every single girl was totally worth it. There were a few who were really great human beings, ESPECIALLY the one I've been married to for over 20 years now. She's worth more than all my family and friends (JW or not) combined and more.
Don't hang all your JW stuff on her, that's too much. You need to be in a mental state where that stuff doesn't even matter or you're putting more on her than she deserves (been there, done that).
As for your parents being around their grandkids, they're an amazing tool in getting your parents to accept you and your loved ones. Those eventual kids are yours, not theirs. You have the power there. If they want to be in your children's lives, they have to be so on your terms. As your kids get older, they'll understand and appreciate you even more for that stuff (again, speaking from experience).