My long term friend just confessed his feelings for me! while hiding a 3 years secret relationship.

I need to get this off my chest because honestly, looking at the whole picture just makes me sick to my stomach. I had a close guy friend for years. Our connection was really deep, and last year when our dynamic shifted, I decided to be honest and told him I had feelings for him. He admitted he felt the same, but stalled giving me the classic "it's just bad timing." I asked him directly multiple times if there was someone else in the picture. He repeatedly swore there wasn't. Right around that time, I hit a wall with severe work burnout and a nervous breakdown. Being that exhausted and vulnerable made it impossible to see things clearly, and he stayed just close enough to keep me hooked. Then, the full truth came out: he had a secret girlfriend for three whole years. It gets worse. She knew about our friendship and suspected something was off, but instead of leaving a dishonest guy, she stayed, constantly fought with him, and blamed "male female friendships" rather than holding him accountable for lying. As their relationship was falling apart, he decided to test his options. Before even breaking things off with her, he reached out and asked me, "If I proposed, would you say yes?" He was literally calculating his next move and setting me up as his backup plan while keeping me completely in the dark. When he finally confessed everything, he sent long, regretful texts about how he "should’ve chosen a path sooner" and "hated seeing our connection end like this." I refused to be anyone's dirty secret, backup option, or scapegoat. I told him straight up that we are done for good, kept it brief, and shut the door completely. No second chances, no looking back. Losing a years long friendship hurts, but walking away with my dignity intact was the only real choice.