Just for a clarification, I believe the failed save would be round 7 of my rage. I have Extended Rage which means I have a total of 14 rounds of Rage. So there are 7 Rounds to get help before I die.
If I had made the Will save, I was going to run away and try to heal up a bit. Sadly, it was not to be.
I will be going on a vacation from Sunday, the 20th, through the following Saturday, the 27th. I should have some access to the internet, but I am not sure how much time I will have to post. So please feel free to bot me as needed.
@Fash I started to second guess my ruling whether Manyjaws was continuous damage - which is the only kind of damage that requires a Concentration check. The usual example is Acid Arrow, as the acid continues to eat away at the target over the course of two or more rounds. This is the part of the spell description that makes me think it does NOT fall into this category: "Each round on your action, each pair of jaws automatically hits its target and deals 1d6 points of damage, or half that amount with a successful Reflex save."
That indicates to me that the damage is not continuous, but rather happens during your action (so long as you maintain concentration) on each round as repeated damage. It'd be the same as if a target was subject to the damage sustained by a Wall of Fire. Or if an owlbear has got you in a bearhug. In the latter case, spellcasting while grappling would apply, but a second Concentration check for taking damage during the owlbear's turn wouldn't apply. Anyway, besides my own interpretation I found this online post about it as well: Repeated Damage vs Continuous Damage
In the current situation, the point is moot as you succeeded on the save! But I do want us to have the same understanding going forward for sure. Also, I'd definitely rule that Feeblemind wouldn't have allowed you to keep concentrating on an active spell, since you wouldn't have any idea of how to cast the spell or sustain it.