Incidentally, I just learned that there's apparently an official document out there that includes backstory information for most of the characters from the original psychonauts... Including Boyd's backstory in detail.
It hasn't been confirmed to be canon, but it was used as a reference document while writing and recording dialog and some of the information was reused in the sequels. (Other bits have been contradicted, however)
If Boyd's backstory as laid out in the document is canon than a lot of things that were off about the Milkman Conspiracy make a lot more sense.
(And everything about Oleander's backstory makes perfect sense with his characterization across all three games and ties his being rejected from the military for being too short back to his initial trauma from the bunny slaughter)