Firstly, who told you that your prior payments wouldn't count toward PILF? If it was anyone other than FedLoans, call FedLoans ASAP to be absolutely sure. It's sad, but there are heaps of servicer shenanigans going down in student loan repayment right now. FedLoans is the direct servicer and the only people who can actually certify you for PILF, so talk to them ASAP. They'll probably ask you to fill out qualification paperwork -- I just looked it over last week (but didn't complete it because I hate working with FedLoans) and I don't remember anything about needing to be in an IBR program for payments to qualify.
Secondly, I'm nearly 5 years into an IBR plan with PILF. I am gritting my teeth and crossing my fingers and hoping and praying that the program either doesn't change before I qualify for forgiveness or that they grandfather me in. If there's a major change in the program, I am probably screwed. My balances are higher than yours (so paying them off in 10 years wasn't reasonable) but like you, my payments don't entirely cover the interest, which means my balance grows over time. If anything happens to the program before I hit my forgiveness date, I will have to repay MUCH more now than I would have when I graduated.
Also, it looks like the forgiveness is not going to be taxed as income, but we don't know that for sure, so it's another thing to watch.
I think in your position, I'd probably switch to either PAYE or REPAYE (which ever was more advantageous) and then pay the suckers off. You'd pay them off free and clear in about 5 years, if my back of the envelope math is correct, rather than waiting nearly twice that time for a PILF payoff, and dealing with a whole lot of uncertainty.