This isn't actual polyamory and it's pretty much never going to work for that reason. What you've portrayed is people who are trying to have multiple relationships at the same time by the rules of monogamy. You can't "fix" your marriage by opening up, but you can expand a healthy one to include other loving relationships. That's what actual polyamory is. It's a whole different mindset and relationship dynamic than monogamy. If you don't know that and embrace that, of course it's not going to end well.