For now you may have to go with shorter A times if his sleep is that badly disturbed with the pain. I'm not a fan of lots of meds either, but the Baby Motrin saved us when Josie was teething, as did Orajel once she got used to it. When she didn't (or doesn't, still!) get her sleep, she's a MESS, so getting her some sustained sleep really was key to us getting the day off to a good start.
If your DS is already waking up tired, you might try getting him back to sleep straightaway in the morning and see if he'll do another sleep cycle for you, and I'd probably let him nap as long as he needs to for at least the early nap(s) while the teeth finish their torture. Lengthening A time and shortening Sleep while his night sleep is so awful might be more than he can handle right now.