I'm not big on the whole "push them away" thing. To me, little, IRRITATING, meaningless things, "push people away." Not putting the toilet set back up. Not brushing your teeth before bed. Being a poor communicator, talking about yourself all the time. THAT kinda stuff.
"I value myself too much to live in an open marriage, where my husband is cheating on me and lying to me about it" is a BOUNDARY, or at least I would HOPE it is with you. If that "pushes them away," then "so be it," I say, and GOOD RIDDANCE!
If I lived with a gambling addict, and they refused to get help and insisted on squandering the family's finances with their addiction, and I said "I love you, but I can't live like this. You need to get help," and if that "pushed them away" . . . .then SO BE IT.
I think the whole "it will only push them away (together)" is a load o' manure. "a)", SEE ABOVE, and "b)", THEY'RE ALREADY TOGETHER ANYWAY!!!!!