"Sometimes, he squeaks a note or so and I'll ask him to redo it or play it slowly - should I leave him alone?"

Probably best to leave him alone -- adult, especially parental, over-correcting can be really offputting to a child. Or leave it to his taecher to correct (or not, as the case may be).

His practice aversion sounds about right for a 10 year old. When my daughter was his age, I sometimes could trick her into practicing (fiddle) by starting to practice myself and playing things on the banjo that I knew she like to play as duets. By the way, it won't get any better when he becomes a teenager. At 16, my daughter will practice if she has a paying gig coming up, or if I threaten to take away the car keys, but not otherwise. And despite this, she still thinks of herself as a musician and still talks about minoring in music when she goes to college.