I am an F 1 Student with my OPT (optional Practical training) which started this month ( July). I am legally allowed to reside and have a driving license in the US until July of next year. If I were to marry someone who is currently not in any status, I understand it may be a little complicated but would he be eligible for F2 dependent visa and be able to obtain a driver's license for as long as my OPT is valid? He is already in US.

You soon-to-be spouse must maintain his legal status until I-539 is approved. If he's already out of status, the answer is no.