He sounds pretty gifted to me, but I know some of what you describe is less exciting and more worry-making.
We were pretty worn out by our ds around that age too.
It was just incredible if I got 8 hours of sleep because it just didn't happen. Things were especially bad if we hadn't made a point of wearing him out with physical exercise - just trips to the park, trips to the mall to run around in one of those play areas, etc.
When he started preschool that was a bit better and then even better when we signed him up for sports.
Both of my children exhibit some of the more worrisome behaviors you list, but neither are autistic, although some strangers have asked about my ds! My dd is the head banger, but this just recently started. I think she knows it freaked me out very badly the first time she did it, so now she pulls it out of her 'bag of tricks' from time to time.
That may be one of the biggest tools to add to your parenting skills: poker face! Really I think these children realize more quickly what are the buttons to push and enjoy/need the attention (sometimes, I know it depends on the child) and they know how to push those buttons more effectively.
For instance - deal with the toothbrushing in a calm but firm manner. Get it done; this goes better if there is a second adult available, one holding the child gently and one brushing, but over the course of a few nights you will probably notice better compliance. You are in charge!
