I had one, never shot it, but my FiL has one and takes it out every year. I have shot that one a bit.
1. Seemed accurate enough. I didn't have time to test out various loads with it or anything, so who knows where it could have gotten. Been awhile, but IIRC it was 2-2.5" groups at roughly 100yds. He's happy with it and is confident in it enough to take it out for whitetail, so I reckon that's all that matters.
2. Not sure what you're going for, not many parts to it. Certainly didn't seem like it was going to fall apart anytime soon, and the finish on it was just fine. The ramrod seemed like pretty cheap plastic though, so he got a new one.
3. Pull off the barrel, stick the breech end in a bucket of soapy water, and use a patch jag and patch to pull water in and out of the barrel.
4. Easy as pie. Loading is odd, you slide the action open and put in the primer through the ejection port. One of those primer loading tools would be ideal here. Otherwise, there's sights on it, work ok(he added ghost ring sights), you attach it the same as any other shotgun barrel they offer.
