I guess he died during the cinematics, but well, have tried doing it by adding trigger X to the trigger queue instead of running the trigger? That way, only one of the triggers will run. first thing you do is maybe making heroes having full hp, locking "game ended" variable and such.
I beg you pardon, thats just what comes to my mind but I have not looked into the trigger: you may have already done it.
by the way, winnable chapters without cheating: 1, This one (99 load games), The Young princes' and the four lanes of attack waves
This one may be the hardest of them, but I really liked how you made his weakness buff and ability. I am impressed ^_^