A 100# tank is its rating for water, and it can only be 80% filled for LPG.
Butane has a specific gravity of .601 and Propane is .495 so it would hold 100# X .80 X .601 = 48 lbs of Butane and 100# X .80 X .495 = 39.6 lbs of Propane.
70F – 30F = 40F DT Butane
70F + 44F = -114 DT Propane
48# X 0.39 SpHt X 40F DT = 749 BTU
39.6# X 0.39 SpHt X 114 DT = 1761 BTU
749 BTU / 165.6 BTU = 4.5 lbs Butane vaporized
1761 BTU / 184 BTU = 9.6 lbs Propane vaporized
-22” Hg is about the lowest practical pressure to run a TRS-21 without running the piston rings dry and according to the calculator at Boiling Point Calculator , at -22” Butane boils at -5C/23F and Propane at about -45C/-49F.
Ummm could you elaborate on the last question?