You probably already instinctively know this, but it's likely that your son being with you full time would be a good thing for him. A boy in his teen years needs his dad (parents really, but dad is very important for him to learn how to be a man; mom to learn how to have a relationship with a woman, and dad again to see how to treat women and people in general.) Stability for a child is very important and let's face it, you're the stable parent for the foreseeable future.
If you can find a way to make that happen, gently, it would be a good thing to work toward.
The obsession with the ipad etc? That's fairly normal for kids these days. But as a parent, I suggest that grades are still the green fee to getting more responsibility and "toys". When you're in a position to assert that, it would be difficult but welcomed.
Hang in there, Wet. There's more to do.
AJ
"Our lives begin to end the day we become silent about things that matter" MLK Put the glass down... "Yesterday I was clever so I wanted to change the world Today I am wise, so I am changing myself."