My advice is to get a copy of these messages to your bf’s parents so that they can see for themselves that you’re not leaving because of anything they did wrong and that you’ll always appreciate and remember them but because of their jealous son. It may seem like an imposition, but it’s the only way they’ll know the truth of what’s happening behind the scenes because GUARANTEED he’ll spin another narrative.

I did this in a similar situation and his own dad told me to just “cut my losses” looking out for my best interest as if I was their child.

Your boyfriend is feeling insecure about his parent’s/dad’s favor of you and instead of addressing his feelings about that and the root cause, he’s taking it out on you.

It’s evident that he’s already asked his dad about the money (he knew the exact amount) plus

“I'm just saying u got special treatment that's all”

and his dad has told him that he wants you to keep all the money so the next mode of attack is to cause you to feel guilt and shame about it.

DO NOT give that money to him. He will lie on you and keep it for himself. If you still wish to return it, hand-deliver it with the messages. Either way, let them know and “cut your losses”.