OK, few hints:
folder "sbps" contains SQUADS (riflemen, tommies, Volks...you name it)
folder "ebps" contains ENTITIES (individual soldiers = soldiers that are in specific squads)
That means that you can have squad which consists of different entities e.g.: 1x Ranger, 1x Lieutenant, 1x Stormtrooper, 2x Folks and 1x KCH - this is not present in the mod but it is possible (just an example).
HPs can be set for each entity
individually in its file.
I know that the Haupsturmfuehrer calls the unit into the game and I found his ability_06 to be abilities\squad_submenue.lua
That is not the call-in ability, this one is the button that "swaps" the ability sets for some units. "ability_x" (x = a number) doesn't say where in the unit's UI the ability is placed. Placement of an ability is set individually for each ability in its .rgd file.
I cannot explain to you everything I know because it would be many pages of text and it would take me lot of time which I don't have, however search the internet for basics of Corsix modding - the information is out there.
relic news forums is a good place to start