In-fighting was a staple of 1 and 2, use it to thin the ranks.
I'm pretty sure you're correct on Hayden being the Seraphim, the voice is the same (not necessarily proof in of itself) but the maykers are are high tech race, the name is similar, maybe he told the real Hayden how to make the mech, but it's actually the Seraphim in it pretending to be Samuel still. He knows way too much about maykr tech for it to be a coincidence. Coupled w/ the fact that Vega was the Father that disappeared when the Seraphim did.
And I just found out the collectable toys are basically a model viewer for the demons, give you a nice up close to see the detail on things you usually leave as a red paste.