I think that IF Valenzetti were still alive, he would be either 1) On the island or 2) Attempting to get there.
Also, this show puts a lot of stock into the actors and characters, so if Valenzetti were in the show at some point, I don't think it would be someone we've already seen saying, "oh, yeah, and that's me".
However, I disagree that the number sequence and the equation itself are wild goose chases as far as discerning the plot. I believe the opposite, that those numbers and the research pertaining to them are the only really informative aspects of the plotline. Everything else centers around ithat.
I mean, all the other data we have could be viewed as lies or hearsay. The whole different time-line thing, all of Ben's B.S., and all the propaganda on those DHARMA tapes; none of it is conclusive.
The numbers are the only "constant" for the entire narrative, in other words.
All we KNOW as far as unbelievable things is that they made an island vanish. If you'd given Houdini unlimited funding, I bet he could have figured out a way to do that.