No he hasn't, the HPI check was clear. All dealers worth their salt will check all their cars against the register and if it comes back as clear - it's clear. What the dealer is guilty of is valeter's who haven't done their job properly. p**s poor cleaning job leaving glass under the seat and no excuse whatsoever for leaving glass in the door pockets! That either gets rid of evidence from a known accident or alerts the dealer to a possible accident he didn't know about.
OP, did you test drive the car before you drove it? You should have picked up on the pulling issue then, surely. Tyre position means nothing as they're easy to swap, as you've just found out. It's quite possible the car has been in an accident with a wall or such and the owner has chosen to pay to mend it instead of informing the insurers. But if the previous owner says it hasn't been in an accident, and it's not on the register, the dealer has as much chance of knowing when he bought it as you have.