I accidentally dropped my bf's vape and broke it. I apologized profusely and offered to pay for a new one
Why are you going  to pay for him?
I didn't want to upset him because I'm done with that relationship, but I wanted to appease him for my mistake.
It's good to take responsibility when you damage someone else's property. That you're doing it after a breakup is even more admirable.
I just want to be friends with him and not get back together.
I really think you did the right thing, more people should be that way. I think you deserve a friendship with him even if you don't wish to get back together.