Help!?
With the 10x15x4 bearing in place on the bevel drive gear, I don’t have enough clearance to install all the pieces and screw it shut.
Check your printers tolerances?
Looks like the bearing wasn’t seated all the way in the housing. 
Do these housings and gears need some sort of lubricant?
Grease them.
Like, just a little grease or fill the housing grease…?
Just a little.