What is/are the standard pronunciations for AMEN and ABRAHAM, respectively????

Hi, Maly - and welcome!
In the UK, AH-men is the most usual (although I have sometimes heard AY-men and, rarely ay-MEN)

The OT sheep-farmer is, so far as I'm aware, always AY-bra-ham. The 'a' in -bra- is usually a schwa; otherwise it would be short, like the 'a' in 'cat.'

This is an interesting question - what brings it up?