no, he didnt 'have to' park where he did - but that is irrelevant - he did park there ... and he was entitled to.
for all you know someone else may have been parked outside his house when he arrived home, who had since left, so he parked where there was a gap...?
it sounds like you have tried to squash your car as close up to his as possible without hitting it, just to annoy him in the hope he wont park there again.
you cannot say that you had no choice, as presumably there is a whole street there that you could have parked in.
as i say you have no more rights than him to that space, and doing what you did would seem to have caused a problem.
when i say 'threat', i mean he did not say he was going to hit you or anything, he said IF you had hit his car, you'd know about it - it is agressive behaviour i agree, but not strictly a physical threat, more warning you to be careful and not to play stupid parking games with him again.
his size is irrelevant.
he could argue that saying 'you'd know about it' meant he would call the police or sue you ... point is you cant really say its a physical threat.
(for what its worth, he probably does mean he will hit you, but thats not the point, he will argue otherwise)
as i say, your best bet is to let it go until he does something definite.