There's a lot going on here - definition of a catch, touch base or tag runner, secure possession, voluntary release, runners lane interference, legality of attempt to avoid a fielder in the immediate act of making a play, willful or incidental collision...
Even in #3 scenario - was the tag before the foot hits the base? The ball is still in the glove, so it seems we have a catch and now have involuntary separation of the glove by an act of the runner. How do you penalize the defense for that (other than of course judgement of crappy throw by 3b ;-)). In other such collisions (say at the plate) if the ball leaves the C mitt, yeah sure safe, but the ball is still in the mitt. It's great fodder to ask a room full of umpires and see how many opinions you get ;-).