OK. You can file to modify custody based upon the child no longer living with the custodial parent. HOWEVER - if child services were involved when you were in rehab etc., you may need to prove that you're now fit.
You need to file where she lives. Check with the local court about appearing telephonically - many courts are allowing that. However, you should also prepare for the grandparents to file for custody too given that they have something akin to status quo on their side OR for Dad to suddenly reappear and fight your custody petition. If you can't appear telephonically you need to either hire an attorney to represent you in Ohio or reconsider your options.
The bottom line is, I really think you need to do whatever it takes to hire an attorney in Ohio, because this could become a long expensive custody battle. I feel I must warn you of that. Plus, you're asking to relocate the child out of State. That in itself can be difficult.
How old is your child, incidentally? Is it really in her best interest to be taken from what she knows as home, school, etc.,? I know it's a hard question to answer, but you must consider that.

