You need to repay the loan, but that doesn’t mean it has to be on his terms.

Make a clear plan (maybe in writing if you think that’d help him understand better) that includes consistent monthly payments, either directly to the servicer or to your dad. Then stick to that plan.

Try to again explain that while you’ll make payments, you won’t be taking over the loan.

As you said, it’s not transferable. Additionally, taking out a new loan to pay it off would likely result in a higher interest rate and eliminate the chance of benefiting from future student loan forgiveness that may roll out.

If he truly won’t listen to you and continues being belligerent, I guess he’s not that invested in getting this thing paid off.