11 y.o w/ fecal impaction, verified via x-ray, and repeated vomiting for 7 wks. Tried oral laxatives, otc enemas, and enema in ER. Any other options?

Gastroenterologist. This serious problem is best handled by a gastroenterologist for diagnosis, treatment and a maintenance dietary and bowel management program providing there is not a structural or mechanical abnormality causing severe constipation and bowel impaction. Perhaps adding a daily medication like senokotS in addition to proper daily water and fiber foods and supplements like psyllium would help.
Manual disimpaction. If medications are not working it may have to be done manually but this would obviously be traumatic for an 11 yr old. Worth discussing it with your doctor, can be done under sedation.
Yes. You can try Miralax over the counter medication without test and smell. With a lot of fluid like water , juice and other liquid. Daily for 2-3 weeks. Start with maximum dose: measurement : cup on top. Good luck. .