I give him advice b/c he asks for it, or try to uplift him b/c he tells me he's unhappy (these are just examples).

When he relates his OW woes to you (which I think is a good thing for you to become his confidante), instead of giving advice or lifting his spirits, have you thought about just letting him go through it himself, with you perhaps having him self-reflect, in order for him to draw the answers out from, and for, himself? As in this manner:

H: "OW twists every other thing I say and uses it against me. What can I do about that?"
T: "That must be terrible. How does that make you feel?"
H: "Like she has some sort of agenda... I mean, it's like she's looking for something to attack me on."
T: "Why do you think she does that?"
H: "I dunno. She's just mean to me sometimes, for no reason."
T: "So, what are you thinking of doing about that?"
H: "Not sure. But I know I don't like it."

and for all we know, that leads the way for H to reflect internally, perhaps drawing closer to a conclusion that OW is not compatible with him, nor the person she originally presented herself to be.

Let him sink to the bottom when he's discussing these matters; save the positive uplifts for when he's reflecting favorably on you and your relationship with him. Subtly therefore influence him.

I didn't not invite him b/c he'd choose not to go, I just didn't invite him b/c I thought... that it might be awkward for him as well.

That's still in the realm of doing his thinking/making decisions for him, isn't it?

I tell him if he asks about things.."I'm not sure b/c I am not you, but this is what I am feeling or thinking

I like that "I am not you".

H said he may stop by tomorrow night, if for no other reason than to make sure the car we sold is ready to be picked up on Monday...not sure why he said that the way he did, maybe to make me feel bad or whatever

He probably said it with no intent toward manipulating your feelings. It may be he's using it as an excuse to come by.