The answer to your final point about Pension Credit, OG, is that the 'rules' assure that everyone of applicable age get a minimum amount - currently about £148 for a single person of £220 for a couple.
Now, if you are one of those men of an age where a female of the same age (call it P) would be able to get their State Basic Pension before age 65, you may be able to claim pension credit as a stop-gap between age P and age 65.
So, for example, a man whose 65th birthday is in the summer of 2018, doesn't get Basic State Pension until then. But a women gets it in about February 2018. In theory, one could get Pension Credit between the two dates.
However, its means-tested, so you'd have to be not-working (much), not yet drawing private pension and not have investments over £10k.
The third point is the killer.