Well, revamp is a mod in the game, it is the one that controls villager behavior. I'll have to take a look since I have been running a server and had no issues like that. When you see that message can you try to pinpoint the chunk to see?
I agree that the infernal mobs tend to have rather high hitpoints, I'll take a look at adjusting that to see what kind of cap to place on it, though does make for a challenge getting started (Had one true infernal (orange name) in my SMP that was causing me some heartache until I could at least get a wall up, lol)
For middle earth, you need to craft a gold ring (9 gold nuggets in a circle) and toss it in lava, but keep in mind that mod only allows one ring portal, so make sure the place you put it is definitely where you want it.
As soon as you let me know a bit more on what you find at the specific location of that error on your map I can try to replicate it.
I can say that it looks like it will be a mod that doesn't make it to 1.7 but I have found a better alternative for that version.
Thanks for the feedback!