Most of what you say seem to be things the parents are ok with...and as there is limited contact with others theres no real effect on anyone but the parents so its more about parenting style and if the parents are happy with it theres nothing to be resolved.
I think most parents 'sometimes' argue in earshot if not in front of the kids. It would have to be more than sometimes for it to have a significant effect on him.
Not socializing at 4 isn't a bad thing, he's with his parents all the time (if little contact with other kids he can't be in nursery or childcare so assume at least one parent stays at home with him). Many 4 year olds are not ready to socialize.
I'm a bit confused how the sharing and hitting is showing up as a problem if he has limited contact with others and has no siblings. It would be more a thing that happens very occasionally and therefore not worth making a big deal out of, though when he starts school it could become a problem. Certainly the play fighting with dad, for a boy in particular, is positive. I have to say when my son (also 4)'fights' with another boy so long as the other is giving as good as he gets I step back...boys bash each other, they consider it fun.
What we think of this childs behaviour isn't relevant, unless it affects others (ie he bullies other kids) its only what the parents think that counts.
