Wider Tyres and lower pressures alone make a big difference to ride quality,
if you can get wider ones on.
Is your seat comfortable on these rough surfaces or is the bike just too ratly
and vibrates you to bits.
I find a slightly Longer wheel base helps, a heavier bike usually doesn’t
get skitso compared to the very light models when you hit a rough patch
at speed.
I am looking for a steel framed bike too, to build into a rough road warrior.