I know he could be one of the great loves of my life, and vice versa, but I am not sure if I am just setting myself, and him, up for heartache. I have told him I would rather experience loving him than not, despite the heartbreak that could ensue.
That sounds kinda selfish to me. I apologize if that is Hard to Hear.
He is your friend. He's newly divorced. He ultimately wants monogamy. So why are you even going there and adding to his burden? You don't mess with fragile people. They don't think clear/right.
Even if they say they are.
If you are not sure if you are setting him up for heartache? BACK OFF. Then you KNOW you are not setting him up for heartbreak! Be a friend first.
A rebound relationship with you could hinder his goal of a serious monogamous relationship in future. It can also cause him great strain. Esp if he's monowired and could be dealing with poly weird jealousies and strain by getting involved with you. He's never been in a polyship. This is NOT the best time to go off exploring that ethically.
What is best for him is the continued support of 4 friends through this transitional phase of his life and minimal drama. Don't rob him of this.
If he's your friend, don't put him in this spot to begin with.
He can find his warm body rebound person elsewhere less complex. I totally get the need for the warm body thing post break up. But YOU don't need to be that friends-with-benefits person. Keep it in the friend bucket despite your crush. And be supportive through his divorce settling in thing as a friend.
A good friend would not put you in mental/emotional weird.
Just because you crush on someone doesn't mean you have to let them know about it.