I think you've got a better idea of your needs than anyone else. Everyone's situation is different. For me, I'm up to my eyes in deer, elk, and big horns. Not to mention cattle, horses, sheep. I wouldn't shoot any of them with a 22 unless I had nothing better. It will kill them eventually, but they may suffer greatly in the process. If I had to resort to prairie dogs, the 22 would win.
Also another +1 for Mossberg. Pick what appeals to you, but I will say don't be afraid of the 12ga. You don't need "professional" training. 200 rounds and you'll have worked it out. No more sore shoulder. It will come naturally if you put the time in.