I'm really sorry that you are hurting so much.

I think that crying, a lot, is a completely reasonable response to being broken up with.

Seeing her car and feeling like your chest is going to cave in: makes sense to me.

Shoving everything that reminds you of her away into a closet: good move!

I question trying to be her "best friend". I suspect that is going to be extremely painful for you.

She is wearing your ring, the symbol of your love. She wants to break up, but she also wants to keep you.

That strikes me as extremely painful, and grossly unfair, to you.

Either she is in a relationship with you or she isn't.

At the moment, she isn't.

Don't let her keep you hanging.

I suggest you go no contact with her.

That won't be easy at first, but it will get easier.

Regular contact with her will be like ripping the scab off of a wound.

Just like looking at that stuff you put in the closet: Contact with her will interfere with healing.