When did you become aware of his 3 sexual liaisons with ow? Did you discover all 3 at one time or did you 'forgive' him after the first and agree to give your marriage another chance before making subsequent discovery, or discoveries, of his adultery?
The only reason lawyers advise against naming co-respondents is because doing so has the potential to cause delay to the proceedings which may, in turn, rack up the costs of the divorce.
Problems can arise when serving papers solely on the respondent and these can be multiplied when it's necessary to also serve co-respondents, more especially as it's not in their interests to rush to return documents as they can be made to pay the court fees for the divorce hearing.
I feel your pain, OP, and your name says it all, but even if you were to name the ow there's no guarantee that they'd have to explain themselves to their ohs when they received the relevant papers.
I suggest you look to divorce him asap for adultery and talk to your solicitor about naming the ow in your petition without naming them as co-respondents - ie. it came to my knowledge on x date that the respondent had committed adultery with and so forth.
If you can incorporate their names into the particulars of your petition to divorce for adultery, you'll have a document that effectively names and shames your stbxh and the ow should you wish to show it to others.
What a tragedy it would be if you were to set out one fine day to send a copy to your stbxh or a very good male friend, but inadvertently sent it to Mr OW's Surname and address. Freudian slips happen
but the best revenge is to live well.
Would you like to share more of your story here? Others have found it does help to vent in the company of those who understand exactly what you're going through, and you'll never be short of a willing hand to hold yours for as long as you have need of support.
Do you have supportive friends/family in rl? If so, I hope they're rallying round and doing their best to distract you from some of the gloomier thoughts that can prevail when a marriage of some duration ends because of one party's infidelty.