After meeting with the psychologist, occupational therapist, and the school district team we have an official diagnosis - Sensory Processing Disorder.
While I don't think this will be our last stop on the road to answers, it does give us a great starting place. They identified that he is a sensory seeker, especially in the vestibular and proprioceptive areas. (Try saying proprioceptive three times fast...)
He has avoidance behaviors in a few areas, mainly with auditory issues. For Rocket Boy, mechanical noises are especially hard - vacuums, the garbage disposal, hairdryer, our clanky car, etc. He also has some tactile avoidance, mainly with sticky/gummy textures or foods.
The school mentioned that he has evidence of some very advanced problem solving skills and is advanced in some other areas as well. They noticed some of his scripting and rote conversations and stimming, which at the very least was affirming to me that I am not imagining things. They noticed attention issues as well, but they were able to bring him back to task pretty easily.
The psychologist says that the testing shows "autism-like behaviors" driven by sensory issues and possible ADHD. While they don't diagnose ADHD in children this young, she sees sure signs of it especially given the strong family history. I'm not sure that she ran the full assessment that should have been done (actually, I am sure she didn't as she said so herself) but for now we are at a point where we can get OT help and see what improvements we see.
We are working on making some simple changes at home to help with his seeking behavior. I made a DIY "crash pad" for him with a sleeping bag and extra pillows and blankets. I plan to make a post soon showing this little project. While it needs a little tweaking, it works as a quick fix for a kiddo who CAN.NOT.STOP.JUMPING. He really seems to love it and our couch is getting a little break.
We changed around our Christmas lists to include a lot of sensory items, and I'm hoping to pick up a mini trampoline on Black Friday. Trying to explain to family that we need things like fidgets and weighted blankets instead of another electronic toy is a bit difficult, but hopefully they will follow the list anyway.
Speaking of Christmas - here is a little peak at taking card photos with my two Rockets: