Hi Dave,
cant answer your points, but have seen common frogs at 1500ft in the pennines, and not near water, but under damp heather!
Froglets move away from the pond en masse over a period of time, and I guess that approach continues until they find a new pond or a food source or a mate etc etc and are 'happy'!
So they may well spread all their lives, whether uphill or not might be irrelevant.
We might well have just found stragglers of this approach.
But I am just guessing, I'm sure others will know some research thats been done on this.
Or not.
Cheers
Ken