What if someone [Character B] had to have their limb amputated (i.e. their leg got mangled/impaled by tree branches, and both Character A and B need to escape and can't get medical attention at the moment), how long would Character B survive without getting that medical attention?
Sidenote: Character B does have healing powers, however it would be helpful for reference of the general idea of how long someone would survive if they were a normal human.
If the hemorrhaging from the amputation isn’t stopped, they can bleed to death in five minutes or less.
Survival depends on how fast they can get the amputation done and staunch the bleeding. In the old days that would consist of a tourniquet, tying off the main artery of the thigh with a reef knot, then tying off other smaller blood vessels, then stitching the flesh (all without anesthetic, mind you.)
If they somehow survive the blood loss long enough, they’ll still need emergency treatment for shock and to prevent complications like infection, heart attacks or blood clots.