You are not merging. You are entering a roadway from private property. At all times, traffic on the roadway has the right-of-way. And that is regardless of what signage is in the parking lot (stop, yield, no sign). I said generally because he still has to drive with due caution (reasonable speed for conditions, safe lane change, signal lane change, etc.).
That's where accident investigation and interview skills come in. If he hits you in the rear, much more reasonable to assume you had a clear lane to enter when you left the parking lot. If he hits you in the driver's front fender then you are going to be at fault 99% of the time. Unless it's night and he has no lights on or was traveling at double to posted speed limit and I see some evidence of that (long skid or yaw marks, witness testimony, severe vehicle damage consistent with high speed). Everyone your age who gets in an accident says OMG HE WAS FLYING. No, it's your cataracts, you 183-day Florida resident.