It was a cute friendship, but not a balanced one (at least feels to me). She was good for him. But what came in return?

It was cute when they were young, but then things got complicated

I think there adorable as freinds

How was Severus unhealthy possessive again?

Not getting over her after several years, basically walking over James' body and then hugging Lily's body unhelpfully and then still not getting over her many years after her death

He physically hurt her sister when she showed negative reactions towards them (this might be an accident though, so you don't have to count it if you don't agree), literally said he won't let Lily not be enemies with the marauders (this scene, to be more specific):

"Snape's whole face contorted and he spluttered, "Saved? Saved? You think he was playing the hero? He was saving his neck and his friends' too! You're not going to—I won't let you—"

"Let me? Let me?" Lily's bright green eyes were slits. Snape backtracked at once."

Tried to debase the marauders' reputation multiple times because of it (along with wanting to stop the bullying, but using a spell that could be deadly on your bully is still not a very nice thing to do. Or trying to get in the shrieking shack, etc.), threatened her to sleep in front of Gry common room if she doesn't talk to him even though she made it clear that she doesn't want to see him, tried to save only her life and not giving a crap about the people she cares (her 1-year-old child for example), etc.

That’s because he didn’t like Petunia, not because he was possessive over Lily

I know, that's why I said don't count it if you don't want to

I chose the first option. I don’t know how they would have been, had James not been there. It could probably have working out fine I guess, but I don’t know

First option