Fantastic write-up Sarge!
I was thinking a bit more about the magic and I might make two more suggestions:
1. For more of an "unknown" feel I might take the spell check list away from the player. Just knowing that a high roll is good and a low roll is bad is probably enough in my estimation. Here's why I say this, there might have been added another level of trepidation and wonder when I was trying to "sleep" that giant if I didn't understand exactly what a high roll might net me. It's very similar to what the "cruddy" table does I suppose, it adds this "what happens next?" vibe that's pretty mysterious. Yeah, it might put a bit more work in the lap of the DM, but I also think that it might allow the DM a bit of wiggle room when things go drastically south and they're not necessarily as blood thirsty as the game calls for.

I know, I know, sacrilegious.
Actually, now that I think a bit more carefully about what I just said there, it might be a little too much work for the DM. Each spell has a chart, and that would be a total PITA for a DM to be switching between charts like that. Let me cogitate a bit more on that. At first blush I'd say a "universal" chart might work. Something that states "1 = way badness, roll on the cruddy chart", "2 - 11 = fail and lose it", "12 - 15 = 20% increase, roll on chart II", "16 - 18 = 40% increase, roll on chart IIA", etc. Still sounds like a lot of work though... Hmmm, maybe it's not worth the "feel". Thoughts from some of you luminaries out there?
2. And on that same topic, I might also keep high = good throughout the system. In other words, if I roll a '1' on a magic check, then another '1' is bad, not good. Just subtract spell level instead of adding.
I would have relished the chance to look a LOT more closely at each of the character sheets pre-game. I had the opportunity but I was too busy chatting away. The cleric sounded really cool. Sarge played him well and in defense of the system, I for one saw each of those "heal" rolls and like I said earlier, he never rolled lower than a 15. That's not a rules issue as far as I know. If someone rolls like that, they deserve to be rewarded.
Heck, Harley rolled poorly for a large portion of the game. For which I was thankful. I have the distinct feeling that our party would have ended up as paste on the end of a large iron mace if it wouldn't have been for some fortuitous rolls on our side and some poor rolls on the DM's.
When Joseph and Harley spoke to "balance" earlier, they weren't kidding. The game pulls no punches in that department (i.e. Not linear at all). Our scenario really forced us to do a couple things that I certainly wouldn't even think of in a 4E game, we played the gorilla tactics card while trying desperately to keep 7-Fingers in check. Not an easy thing to do btw. But it was an eye opening experience as a third level character w/ 7 HPs.
Come to think of it, when Harley said "giants"... I almost laughed out loud. I did that funny little cartoonish double take at my 7 HPs and thought "We're dead". But hey, we made it.