I appreciate the bit explaining the actions of the non-possessed animatronics in FNAF2. That makes a lot of sense. The question I have, then, is how did the child possessing Foxy get murdered if he wasn't lured away by an employee in costume like the other kids (excluding the marionette)?

I'm also having a hard time piecing together when in the timeline of FNAF the Purple Guy came back to chop up the animatronics and inadvertently release the childrens' spirits. If we look at the newspaper articles that sometimes appear over posters in FNAF1, it says that the suspect was charged for the five murders at Freddy Fazbear's Pizza (and was likely framed for it, since the purple guy was able to come back, period). Even if we use the paycheck to guess that the events of FNAF1 took place in 1993, someone in jail for murdering children would be in for life, not released after 6 years. Then again, the articles only say that the suspect was charged, never convicted, so it's possible that the surveillance footage showing Purple Guy luring the kids away to be murdered was somehow not a viable source of evidence.

My main reason for guessing that the Phone Guy's message that "We had a spare in the back, a yellow one... Someone used it... Now none of them are acting right..." does not refer to Purple Guy's demise mainly stems from the fact that it's pretty clear that the FNAF3 death minigames take place in the FNAF1 location (credit to /u/CDMAN2 on that image), and since the animatronics in FNAF2 have a strong reaction to that particular incident, I'm going to guess it was to compensate for the additional murder(s) taking place (possibly the marionette "giving life" to Golden Freddy, who is only active on Night 6 of FNAF2).