I know you said rifle, and I don't want to dismiss that, but I would suggest a pump shotgun to be the best all purpose.
Shoots slugs to 150 yards with a rifled barrel. Can be scoped also. With a smooth bore you can shoot slugs with good accuracy past 100 yards. Buckshot for defense, bird shot for small critters.
You can get a Maverick 88 12 gauge for $150.00 new. It is a Mossberg 500 with plastic furniture, and the parts are made in Mexico by Mossberg, but assembled in USA. A rifled barrel costs $100, and a 18.5" Home Defense barrel is $80. You're still way under $500.00.
I have out shot many people with my $150 12 gauge Mav 88 at the trap shoots. I have also hit clay pigeons on the 100 yard berm with smooth bore barrels shooting plain old slugs using just the beads for sights.
I will not go into the which is better, and people want what they want, but if you break down your post you will see that all signs point to 12 gauge shotgun.
We went shooting this last weekend, and I took the new AR-15 Dissaptor, the 44 Mag, the 44 Special, the Marlin Model 60, and the Mav 88. The most fun I had was shooting the Mav 88 and the .44 Mag.
W-8+
e shot clays at 100 yards with the 12 gauge. We shot clays that were thrown with a hand thrower. I shot everything from 3" slugs to bird shot. That includes 3" steel shot, 3" #4 buck shot, 2 3/4" 00 buck. There was a door at the range. A metal door. We shot it from 5 feet with 3" #4 buckshot. I blew a hole the size of my head in the door.
Anyway. What I am trying to say is the $800 AR ended up sitting on the sidelines while t+he $150 shotgun blew $41T up.
Enough already.. I know. Sorry. All signs point to shotgun.