Great outcome!
I had meant to mention the clothes iron before and promptly forgot.

I had a customer bring in a kit build with a neck he had glued in crooked! He glued it with PVA, but I said I'd have a go... no guarantees...
It was the iron and towel trick that worked for me too. Except it took about 12 hours!

The irony (pardon the pun ) was that the kit was a BOLT ON neck! He glued it AND screwed it because "that's what I thought you were supposed to do". Yikes!

Your son should be very happy now! Good on ya!