That's tough, you have to try it both ways. There are a number of deductions and credits that are disallowed filing separately so you will probably pay a lot more tax. You have to think about whether the loan savings offset the tax cost. Also think long term, with MFS you can't contribute to a Roth IRA or a deductible pre-tax IRA, so that impairs your long term retirement savings. You can't claim the credit for child and dependent care (day care) or use a dependent care FSA.
You also need to think long term. Making minimum payments, you might be paying the student loan for 10, 15, 20 or 25 years before it is forgiven, if you even qualify for forgiveness. And at least some of the forgiveness programs, the forgiven loan balance may be taxable income in the year it is forgiven. So you could keep your loan payments low but your taxes high, and then get hit with a big tax bill when the loan is finally forgiven. The rules have changed so much and so fast, you may want to consult with a specialist -- and bearing in mind that some of the Biden forgiveness programs are probably illegal and might be overturned by the courts, and I would not expect Pres. Trump to offer much in the way of new forgiveness programs. (Of course, any forgiveness program that is created by Congress with a law can't be changed except by another law, so you have to look at forgiveness programs in the law vs forgiveness program created by executive order that can be changed.)
