Shotgun plain and simple Prox. They make buck shot with low recoil that is also designed not to pass through existing walls or rooms. Plenty of home defense ammo built with that strategy in mind.

Could also get a 20 gauge. Lighter and easy to hold and pump. Better than nothing and certainly effective.

Again that sound of a racked shotgun can be all the deterrent you need.

You can certainly handle a 12 gauge. They make them lightweight too. So many options