I can't answer the first two, but
3. what if any qualifications does a banking institution have that define it as a cogent source for software? Apple has been developing quality hardware and software for a generation now.
Banks have been developing banking software for a long time. Apple has not. That's not to say their software development skills couldn't be transferred successfully, but for the moment I'd place higher trust in banks who understand quite well what the financial implications of poor security are.
FWIW I think a handful of systems is better than 4000, and is also better than 1 or 2. I like for instance that the US has a few credit card processors; enough to gain the benefits of competition but not so many that it is impossible to support the vast majority of users.