As far as his taking responsibility for his disorder, connect it to things he likes to do- if he doesn't take the meds, go to appointments, etc, then no video games, time with friends, etc- there's a risk of video induced seizures without medication, and being around friends may be good, but not if he's unsafe without meds...... it's up to him.
If Topamax is giving you nightmares, ask the doc for something else. Let him/her know your concerns and ask for a more tested/used/older medication- those still work....

I'm on exclusively 'older' meds (Tegretol, Klonopin, and Neurontin- though that is more for another disorder, but is an anticonvulsant). I don't get side effects from those at all.