Best of luck. Good decision but yes, a very hard conversation.
I'd do it by email myself, then block him. He's so manipulative and you have such weak boundaries.
If you do speak in person, make sure you can leave easily if he gets too angry and becomes verbally abusive. If he tries the "you're abandoning poor lonely recently widowed me" stunt, remember the bunny and the gay cheating history and don't weaken and stay, consenting to be his new beard.
And maybe spend some time with a good therapist exploring why you were friends for 43 years with this toxic cheating man and found it so hard to see his toxicity even when he wanted to have sex with a man in front of you in a threesome, and hurt you physically. That is not healthy.
