OP, you are being played by both of them, no question.
The only question is whether they are playing you for individual gain, or for a mutual plan of eventually running off together.
Somehow I doubt it's the latter - for the OW. Her politically cool reponse to you (see my post just above) is the response of a PLAYER, but I doubt shes playing for keeps with DH. What would she want with him as a full-time proposition, especially as he'll be worth at least half of what he is now once he's met his divorce settlement responsibilities.
The fact that you send most of an evening texting her is ... fucking weird. For you own sake, stop it You are just torturing yourself - what on earth do you reckon is it going to achieve? For all you know this cool customer is laughing her head off at her power over you. Stop throwing your dignity away - you need it for yourself.
The weirdest bit though is how long she was prepared to text with you. Think about it from the perspective of a innocent colleague:
if innocent, you might be concerned, embarrassed, offended, upset by an unfounded accusation. You'd want the chat to finish asap. You certainly wouldn't be entering into an hours-long chat with your boss's wife FFS. You'd be cutting it short, protecting yourself, referring the wife back to your boss. You'd be making yourself scarce, & less noticable, not more.
I think the likeliest theory about OW is she is enjoying the power of having her boss in her thrall, & that she enjoys playing head games.
DH is a fool, & he is being so crazily disrespectful & cruel I don't know how you are staying in the same room as him right now. Let alone waiting for him to "see sense" or "come back".
What happened to your cooling off period btw?
And what resource is being put in place to support YOU through this horrible time? Do you have a counsellor? Are you doing any learning like assertiveness training? Because - wrong & twisted as DH & OW are, how on EARTH is it that you are unable to find your anger, your self respect, your dignity, & kick them both to the kerb?