Your analysis is interesting. From what I've read, a lot of sex offenders recognize that they have a problem, try to control or suppress their urges, and ultimately hit a breaking point and do the act that satisfies their urge. If Suspect 1 in your analysis was indeed the offender, then he might have fit that psychological profile where he realized acting on his urges made him a monster and made the correct decision to take his own life rather than continue the cycle of terror. Seeing that he committed suicide on the 4 year anniversary just seems like too much of a coincidence if evidence was already pointing towards him.
Edit: Any idea if law enforcement has Suspect 1's DNA on file to cross reference with DNA presumably found on your old classmate? That's how most of these kinds of cold cases are getting closed.
Re: your edit:
From what I understand, they have tied S1 definitively (this came well after the fact, remember in 1980, dna evidence wasn't anything at all what it is today, if it even really existed at all back them (I mean, they were hypnotizing witness in those days?!)) Thru the hair I mentioned. but they have declined to charge a dead man and dont believe that doing so would be the close of the matter. (Meaning, to me anyway, there is ample evidence tying someone else to the crime (eneter S2))
Suspect 2 was approached as recently as Q4 2018, and refused to answer questions- directing the matter to his unnamed attorney.
As a lawyer, I completely understand that. Theres no statute of limitations on murder. However, as a person, I find myself thinking... if it were me, and I was innocent, I'd tell the cops everything I know, now some 40 years later. Which is to say, his refusal to talk, even now, raises an eyebrow, if nothing else.
Edit- and to add on to that last paragraph... if he has an attorney, then I dont see why - if s2 is innocent- an interview couldn't be conducted in the presence of counsel