Changing children’s last name to biological mom who used sperm donor

[Anonymous]

Among all the legal complications, I think explaining this to the kids would be the main barrier. They love him and they know him as dad. Trying to explain that he isn't biologically their father and essentially changing their identity would be traumatic and confusing.
That doesn't mean that you have to stay in a loveless relationship or home. You can split up, like many couples do every day. You seem intent on punishing him without wanting to inconvenience yourself in any way, and that's not really fair to him or the kids.