Your boyfriend got a judgment against him and didn't pay it.
He didn't have anything for the creditor to go after back then so they waited.
Judgments are good for a long time.
Now the creditor apparently found a solid bank account to go after and has attached it to pay toward the balance owed. That's legal and proper.
That you and he are joint holders of the account makes your money fair game because in a jont account each party's money is also the other party's money.
That the debt has grown by more than twice is because of interest, lawyer fees, and court costs.
Pretty soon the money in the account will be released to the judgment creditor.
That's how it works.
The credit union is under no obligation to help. The lawyer is under no obligation to help. The bank has to follow the court order and freeze and release the money to the creditor.
The reason you are running in circles is that the circles you are running in are the wrong circles.
Unless your boyfriend has some legal grounds to ask the court to cancel the order (and I don't see any) then it isn't going to be cancelled no matter what you do.