I was puzzled and a bit annoyed at Doom apparently thinking the rest of the F4 are dead when he shouldn't after reading issue one, but I've tipped over to thinking it's an act at this point. I'm pretty sure he either created that message from "Reed" (and possibly even the Multisect too) or he's manipulated it in some way to get Ben and Johnny to go off into the universe searching for them. The way he acts in issue two sealed the deal for me, where he basically shows up on Monster Island, is exasperated that Ben didn't get a clue that was aimed at him specifically, goads them into searching harder by going on about how it's probably a wild goose chase and he's not going to bother searching himself any more, and then pointedly drops the word "trophy" that makes Ben think of the real answer to the clue.

I feel like Doom's "This is too rich" in response to Ben lying is actually about the ridiculously ironic situation where Doom is lying that the others are dead because he knows Ben and Johnny would never believe the actual truth when it's coming from him, and then Ben's just turned around and unwittingly convinced Johnny of the truth anyway.