My question is, how...HOW can I let him know that I either want to work on the marriage or divorce (no separating) without him getting mad/defensive.
TS,
I don't accept your premise, and either should you.
Whether or not he gets "mad/defensive" should have absolutely NO bearing on what your decision-making is.
If I could give you ONE PIECE of advice for DBing, it would be this:
Stop operating from a position of "What will he do if I do/say thus-and-such? Will he be angry? How will his reaction make ME feel?"
and instead, learn to operate from a basis of: What is THE RIGHT THING TO DO in this situation? What is the thing that God Himself would have me do, if He were standing right in front of me?