M.D.
I'm a high school teacher...we had a student from the elementary school taking advanced high school math classes...talk about disparity between intellectual maturity vs. behavioral maturity!
I also have a friend with a 4 year old who is off the charts big in height and weight and so people expect more of him than is age appropriate. I admit that sometimes I am surprised by his behavior and then remind myself of how young he is.
I have a 5 year old only child with many of the struggles you mention...he's not seriously advanced intellectually (though he is quite bright), but he struggles with sympathy, empathy and with appropriately handling anger and frustration.
So far all I've done is to point out that I understand your question. The only help I feel qualified to offer is on the anger/frustration topic as it is a real concern with regard to my son...he gets very angry and hits, kicks, says horrible things, throws things, breaks things...this morning he intentionally spilled coffee on the new rug and smiled when he got caught...all because he didn't get his way. (I'm not sure I'm overly proud of my handling of the coffee thing...) Anyway...I have made it goal number one to help him learn to control his anger...probably so high on my list because it may be the biggest reason that I divorced his Dad. I have found that a lot of talk and conversation at a quiet, unemotionally charged time about how to properly handle example situations comes in very handy when such situations arise. When I begin to see his anger escalate, I calmly ask him how he should handle the situation to force him to think about what is happening...at that moment sometimes he does stop, think and act appropriately...other times he doesn't, BUT sometimes he does it "the right way" all on his own now and he never used to. When he does I congratulate him and talk about what he did well and offer him some type of reasonable reward.
That's what I have to offer...hope it's helpful.