I wish I could give you some practical suggestions. I believe there are adjustable benches, rather expensive. I'm not sure how one could readjust keyboard height, however.
For what it is worth, the organist at the cathedral, who is is brilliant organist, is a very small person. He can't be more than perhaps 5'2".
Watching him play, his feet reach the pedals with no difficulty.
I wonder how he does tenths.
Good luck--