Chill, man. I never said that it was an absolute certainty that they had firearms onboard. Nor, given the aptly demonstrated uselessness of same on the Moon can I see any justification for them putting any on the LEM. The capsule is a possibility, but not a certainty. (The astronauts were allowed a small amount of weight for personal items. Buzz used his for a communion kit, Irwin, IIRC, brought a tape recorder, whazzis name on 14 brought stuff to test ESP.)
Nor did I state that it would be possible for them to tap into the LOX tanks of the ascent stage to survive. It is, however, most certainly a fact that had something gone wrong on any of the Apollo missions with two men being stranded on the Moon that Mission Control would have done everything possible to get them home again. Witness Apollo 13, where they worked by the seat of their pants to keep the crew alive. The conditions on the stack were nothing that they had simulated, since everyone thought that such an accident would be immediately fatal.