My opinion, worth what you paid for it:
Remington 870 Express, 3" chamber. The pistol grip may look sharp but if you do get one, make sure that you have a shoulder stock too, probably folding. After you've shot it a couple of times without benefit of shoulder stock, you'll see why. The 3 1/2" shells might
be useful if you want to hunt geese but not for home defense. Just not necessary. Short, Cylinder bore or Improved Cylinder. 00 Buck is easily overchoked, unless it's stacked in 2s rather than the much more common 3s.
I would also like to reload my own shells.
That's another game entirely. If you have any general or specific questions.................?