Yeah, once you're in hell you're pretty much stuck there... If you're really getting spanked, you'd probably have to reload an earlier saved-game...
[suggestion - have you tried the search function for Irenicus strategies? Everyone's asked for tips before, and there may be a strategy that can utilize what resources you've got. Defeating Irenicus is NOT the hardest thing in the game - it would be cool if you could somehow get through it without resorting to an earlier save
]