Meds for 28 year old daughter with autism (moderate / severe level)

Hello, I am new to this site. My daughter, Shannon, is 28. In the early days of her diagnosis, we tried AIT (Berard), some vitamin therapy (didn't work), some diet adjustments (limit dairy.. I'm just no good when it comes to diet stuff that takes a lot of time), tried some sensory integration therapy. She was always in special ed and now a day program, needs 1:1 or a lowish staff to participant ratio).  I would say her autism falls between moderate and severe. She will never live on her own, she's like having a big toddler. She's a whiz when it comes to remembering dates and birthdays, but her communication just isn't.. interactive. She is verbal though. She has had behavioral issues (getting very agitated, hitting, sometimes kicking). I don't think it's 'anger' but rather frustration and she just gets in a zone then it's over almost as suddenly as it arrived.  I say all this just to give background.

Back when she was a teen, her psychiatrist put her on Geodon and Risperidone, adjusting the dosages. She had some huge issues in her early 20's, we changed docs, he took her off Geodon and only prescribed risperidone. The more she had behaviors, he upped the dosage until she was on 2 mg AM and 1.5 PM. She gained 100 lbs but her behavior did improve. I hated all the weight gain, but he never would switch her meds.

Fast forward, we now live in NC (where it's tough to get services, but that's another story). We have a doc who is willing to try other meds. She is on Lamotrigine 2x a day (200mg total). She doesn't eat so non stop compulsively any more and seems okay. Dr. also prescribed Trazodone (we used a low dose) and while it seemed to help Shannon at first, then it seemed to agitate her. We also tried Clonidine and Buspirone but have stopped both. We did the saliva/DNA test to see how she metabolizes meds, because what works on others, doesn't seem to work on Shannon.

Right now she's on Lamotrigine only, and, in a way, I wish we had one more med to calm her a bit. She would try Seroquil, but I'm scared of the non stop eating again.

I'm hoping the test results yield some helpful info. Shannon has very sensitive hearing... I'm going to try a listening program again. She hums almost constantly, sometimes much louder than others. We've been around with essential oils, I think I'll try lavender again and see if that helps.

28 years of dealing with autism and I'm just tired!! I don't mean that to sound negative at all. I love Shannon so much and she brings much joy. She lives at home, doesn't sleep the greatest.... it's just exhausting sometimes (I'm sure you all get this)!  I am thankful she's off risperidone, but wondering what others have tried. 

Thank you for listening!