So austenizing at 1500 should get you about 65rc as quenched, tempering at 400f should be in the 60-61rc area (I’m referencing Kevin Cashen’s website). Maybe your low rc is due to making the edge too thin before ht? ie., losing heat on the way from kiln to quenchant?
60-61 should work just fine at the angles we hone razors at, as I understand it.