Max your traditional IRA (FYI, you can't max both a Roth and a traditional; you get $5500 total to split between the two). Then pay the loans down in the order of A first, then C, then B.
...Unless you can refinance to reduce the interest rate below, say, 4% or so. If you do that, stop paying extra on them and invest the money instead.
Personally, I wouldn't use up the forbearance (you can only get it for a limited amount of time) just to be able to pay extra on A instead of B; I'd keep that option open in case of unemployment or something.
Also, negotiate with your employer to get some kind of employer retirement plan (401k, SIMPLE IRA, etc). Taxes on $90K will suck without being able to defer more of it. Even negotiating to become an independent contractor (with an appropriate raise to compensate for payroll tax and loss of benefits) might be worth it, to become eligible for a solo 401k.