Wow, thank you all so much for your support! Sorry to be so late to this, but I had notifications turned on, though I hadn't been notified. Anyway, thank you again!
Since I last spoke, things haven't really improved with my in-laws. My MIL has been referreing me to people as her "son's wife from abroad" and likes to make it very, very clear to people that I'm not British. There have been more and more comments about how our children "won't be British because of their foreign-born mum" and more recently, it's been suggested that I'm using my husband for a passport. We don't have children, and had hoped to start planning for them in the very near future, and I'm glad that this has all come up now so that they won't have to go through it. I couldn't imagine being a new mom, excited to show off my baby, and then learn just how my in-laws feel. I'd be heartbroken, and at least knowing this now, my husband and I can better plan for ourselves and our family.
I've recently sought therapy over the verbal abuse I've dealt with over the years from my in-laws, and my therapist agreed with me that it was best for my husband and me to move away from his family. Like, properly move away to somewhere that would be a financial burden to visit. His family don't have the financial means to travel to the US, and while we're both able to financially make these trips back and forth, it's unlikely we will (at least just to visit them). If anything, we'd quietly fly over and see friends, maybe go somewhere for a holiday, and fly back to the US. We have a place in mind on where we'd live, and we're both able to transfer our jobs, thankfully, so that's a huge mountain of worry gone. My aunt, bless her, is just waiting for the text that says, "Can you pick us up on this day at this time?". She's so excited for us to move.
We've been introduced through mutual friends to a couple who are going through the same experience as us. It's really quite spooky how similar their story is to ours. Knowing that we're not alone has made this easier to go through, and also having the support of others really helps us know we're not insane. Thank you all again for reading, and for your support.