I'm so stressed and I'm freaking out!

I have this really good friend who I've been close to for years....even before he was married we were friends. His marriage is failing. He's separated from her (I'll be honest she's pretty nuts and has some serious anger issues).

As his friend I've always been there for him. Genuinely as a friend. Never sexual. I was always there to talk, give advice, help him when he moved. We never did anything that would make you question our friendship or his marriage. We could joke around and all but I'd never cross a line. If they had a fight and he needed a place to crash, the deal was that if he came to my place, another person had to be there OR he could go to my parents place (they see him as family and another one of the kids LOL). I'm big on doing the right thing and doing the best I can. I'm the first person to say I was wrong and make amends.

Anyways so they have been living apart for roughly 6 months now. They hardly text. They never see each other. I will be honest, he has been spending a lot more time with me. I'm a very organized person. He's pretty nonchalant and goes with the flow and doesn't really prep for stuff. So for instance, he asked me to help him research divorce lawyers. We took a weekend and researched what divorced include, looked at places, left some emails and all. When he had two consultations, I helped him prepare some questions to ask and whatnot just to lend a hand. He was terrified of going so I drove him to the appointment and I waited in the car (was not necessary for me to be in there with him).

When he was looking at apartments for himself I went with him (my mom came once too!)

Long story short. He bought me a ring. No not an engagement ring. Not a promise ring. Just A RING. Which he said he bought simply for his best friend who has always been there for him. It's a Tanzanite stone surrounded by little diamonds in white gold. So it's not a little ring pop. There was a bit of money spent here. I told him I can't accept this it's too much and you're still married. He's like I'm not proposing. Its just a ring to show our friendship.

So I've been staring at this ring for hours now in the box. What do I do? Throw it back at him?? Yell at him? Keep it? It feels wrong. I know he loves me as a friend. But is he subtly working his way up to LOVE? Am I the rebound? My mom googled this ring and the store price is $429. No not a crazy amount of money. But more than you should spend on a ring for just a friend you know?? So please send help guys! I'm so stressed over this