I’ve been testing this, took most of those screenshot above 
Right now to get a map from Trenchbroom into UE4 with HammUEr, this would work
-save it as .map
-open it in something like Jackhammer
-save it as a Half-Life 1 .rmf
-open it in Source engine Hammer
-save as .vmf
and then it would comfortably import into UE4 via HammUEr.