Nice analysis.
I couldn't really spot strong bass differences in nature between UM3X anf SE535LTD but they were slight more present on UM3X so this could be easily circumvented via EQing.
For treble, I tend to find UML3X treble superbly clear but I had to push EQ up to have them loud enough (coming from FX700 treble, you can understand why). On SE535LTD treble are more natural and I didn't have to EQ them up as much as with UM3X.
Amping did really open the SE535LTD treble, whereas it didn't do much for UM3X with my FiiO E7 amp (since UM3X treble were already excellent to start with).
Overall 2 great IEMs if you value separation and mids above all.