John, I completely agree with your sentiment:

...the position I start from, paricularly in view of the many unexplained experiences I have had, is that the subjective alone is insufficient for me to treat experiences as 'the truth'. I have been fooled, or fooled myself, too many times to do so. So I would like some objective evidence for the extraordinary claims that are made. For instance, when someone (such as myself) has an experience of being 'all-knowing', then some small, verifiable, piece of information from that 'all-knowingness' should not be too much to ask.

I believe that the question whether such an experience is 'the truth' is unanswerable; but a much more reasonable question is whether such an experience is valuable, or worth having.

My question then is, what would qualify as a 'small verifiable piece of info...'? As I say, let's put tricky questions of 'the truth' aside. If you had an 'all-knowing' subjective experience, but found that afterwards, for several days in fact, you were happier in yourself, felt better towards others, and as a result you accomplished more things, and accomplished them better, with no downside - would that in any sense validate your experience?

This is a hypothetical question - note the 'if'; also note the 'with no downside'. The problem is that for most of us, our 'all-knowing' experiences did have a very substantial downside, and most of us consider that any happiness and good-feeling we had was far outweighed by the negatives (loss of critical thinking ability, giving our lives and all our possessions to an Indian guru, etc).

But my hypothetical question still stands: If you had a meaningful, powerful even, experience, albeit subjective; and you found as a result that its afterglow made life better, both for yourself and those around you; and there was no downside; would this subjective experience be validated, worth having, worth pursuing even?