This sounds SO much like my Bear (now 5). I started looking into help for him just before he turned 3. I was faced with a whole lot of, "Yup, there's something wrong, but it's not bad enough or enough check marks on this list for us to help you." He has been tested for nearly everything in the book at this point and falls short of all of it by a check mark or two at the most.
The tantrums were helped a lot by using the occupational therapy technique called the Wilbarger brushing protocol (if I remember the name correctly). He went from over an hour tantrums every day or two (on top of about ten fifteen minute ones every day) to one fifteen minute one about once a week and only about 5 short ones a day.
Once he is comfortable in a group setting he behaves well there, but then loses it at home, often for MUCH longer than he was in the group setting. As far as I've managed to figure out it is because he is subconsciously anxious and worried about getting along with people, adjusting to new experiences, etc. Once he is at home, he is "safe" and all the stress can come out.
He NEEDS to eat regularly or it's all over.
This is the kid I used to have to pin down to brush his teeth. Then he'd just fuss. Finally just a month or so ago he is brushing on his own, rinsing and spitting. Getting dressed was the same thing. It just seems to take him longer to mature in some areas than other.
