I agree with Les. I haven't used D3200 a whole lot, but remember the film processing person at the (very good) pro-lab I used to work at always held that the D3200 actually was a true 1200-speed film or thereabouts.
ISO100 exposure can't be that bad, in terms of overexposure you always have latitude. Dilute developer (I use Pyrocat, but Rodinal would be good too) in semistand configuration. If the frames matter to you, shoot one more roll at EI 100, cut it up to thirds or so, and try a few various times with Rodinal 1+100 or similar. Remember that with a solution that dilute, it may exhaust too rapidly, so put plenty of solution into your tank, more than usual.
I recently did this with Agfa APX400 exposed at EI 50 or so. That's a three stop over-exposure. Developed in Pyrocat-MC at 1+1+150 dilution was great and I have fairly normal looking negs that I think will print great.