I have a 75 CJ-5 but mine is "slightly" modified.
Question 1: For my heat riser tubes, the carb had basically steel lines bent and a slight "bump" about 1/2" from the end. The tube simply fit into the riser tube end (your 1/2" steel fitting) and then the connection to the carb held it in place. The bump in the tubing prevents it from going into the fitting too far. If you don't have the original tubing, something like a drill bit stop gage (fits around a drill bit to limit it's depth) would work also.
Question 2: I think that is the e-brake cable termination bracket. The cables from the rear drums end at that bracket, the cables stick through the bracket and the single cable going up to the e-brake pedal attaches there.
Question 3: Both the 30 and the 44 use shims to control pinion depth and preload. According to my 75 FSM, both yokes are torqued to 200 to 220ft/lbs. I'm assuming that all you did was remove the yoke, replaced the seal and want to reinstall the yoke, no gears need to be reset which is an article in and of itself.
Question 4: Yes
1975 CJ-5, AMC 360, T-18 w/6.32, D300, 4.56's, D30 w/Lock-rite, D44 w/spool & FF, 33x12.50 MTRs, full cage, OBA, PPW, and a few other mods.