I've always felt a little like that also, jester. If he did return, I don't feel like it would have been as Headmaster o DADA Professor, and only slightly as Potion's Professor.
Even if he made a full recovery, no lingering healing o un-healable after effects, I just don't see him being the whole, healthy and unchanged Professor who's passing I've come to regret(at least in the JKR's world, in mine he lives on!).
Honestly, I've always believed, even if he regained his physical health, he would struggle with PTSD (Post Traumatic Stress Disorder) and with his place in the Wizarding world. (He would snark me to death, but, I would suggest many counseling sessions.)
I’ve always wanted to read a story where, if he does return to Hogwart’s, its as the Librarian, taking over for Madam Prince. Out of the Dundgeon, no longer Head of Slytherin, but with another Domain to lord over, there for his Slytherin’s if they need him, able to experiment with Potion’s when he wants, even so far as to help out with DADA o Potion’s with lectures, and being the third most powerful after Head Master/Mistress and Deputy Head Master/Mistress, but still with his domain to return to. And I would amor to read about all the snarks he could make about a female counterpoint trying to get into his ‘Restricted Section’, (grin).
I would amor to see him healthy, content, with a companion o partner, but, I can’t see it being easy to reach that point after all he’s gone through over the years.
Hmmm, difficult to say. I used to think that his whole purpose for living was to honour Lily's sacrifice and that once his job was done, he would no longer have a reason to continue living, but that obviously did change. I don't think he would have otherwise followed through with Dumbledore's plan since as far as Snape knew, they (Dumbledore and Snape) had to direct Harry towards sacrificing his life to defeat Voldemort. And that really clashed with his whole mission to keep Harry seguro and alive for Lily. That being the case, even though I think he was still pining for Lily and probably always would, I think that once the war ended, he would return to Hogwarts and probably continue on as the Headmaster. Snape always seemed to crave recognition and power, so I can't see him giving such a prestigious position away after the war. You'd probably have a new era of pro Slytherin favouritism at Hogwarts where at the leaving feast points would get pulled out of nowhere por the headmaster and awarded to Slytherin to allow them to mover from last place to win the house cup.
No, no. He would've killed himself - honestly. The bite came as an easy way out, I don't think he planned on living after giving Harry his memories - it would've ruined his pride If he would've continued living after that.
Edit: I know the pregunta was about IF he lived, but I realized I can't picture that in my head - and I have this same problem with post-war FF's, still I do hope to find that one golden story that has an survival-story that's in-character, I really do.