It would be ashame to fault the pistol if it turns out to be the mags. If you've only fired 500 rounds in 8 years and the mags have been kept fully compressed for most of that time it is really likely that weakened mag springs are your only problem.
The locking back with one round is odd, though. How often did that happen? and, was it a true locked slide or just a failure to feed that held the slide open?
Your mag drop problems might be an overtightened grip screw also.
BTW- I'm no huge Beretta guy trying to defend the gun. Just trying to help you salvage a healthy relationship with your weapon.