I'd be interested, though you got a bit of lore mixed up. Dr. Altman didn't lead the religious movement. He actually actively resisted the rise of Unitology. The beginnings of Unitology, as well as humanity's first encounter with the Marker, are detailed in the novel "Dead Space: Martyr". Altman himself didn't believe the Marker was something divine, but knew full well that it creates Necromorphs and that they're caused by a defective genetic code that's broadcast by the Marker. He discovered that all the Marker wanted was to reproduce, and that the Necromorphs are its failed attempts to do so. The Unitologists didn't listen, though, wrongly giving him the status of saint when really they should have marked him a heretic for resisting them so much and trying so hard to prove how wrong they are. In all actuality, Altman knew more about the Marker than any would ever know, which was likely why he was remembered as the patron saint of Unitology, despite all his efforts to debunk the religion. Altman had even actively communicated with the Marker, which was how he learned its true purpose. He learned that the Markers are sentient objects. You should read the book, sometime. It's quite a nice story and sheds a lot of light on Unitology, which was only hinted at in the games and what was detailed was according to the religious teachings, not actual historic records. It's kind of like how Jesus was most likely a completely different person than the messiah described in the Bible. People glorified Altman, gave him more credit than he really deserved as far as religion was concerned. I don't quite remember how he was actually killed, but I think it was quite unceremoniously by a Slasher. One thing Altman didn't know about the Marker, though, was its origin. He couldn't get that bit of info out of it during the couple of minutes in which he communicated with it.
Also, since this seems to be a prequel to Dead Space 2, would we end up running into Vandal eventually?