I'm sorry that you had a rough time. It's okay to feel jealousy and it can be a great tool of change when you are feeling unfairly treated. Sometimes it's really hard to walk away. I spent six months in therapy trying to work up the courage one time. Going forward, you'll be able to make more informed decisions about what is right for you.
There are a lot of ways to do polyamory. It takes two to define a relationship together. I'm a big fan of RA and ethical polyamory. With the right communication, everyone can get what they want and be a primary partner. I go out of my way to make sure I'm meeting the needs of the people I love.
I feel like the wide and often free availability of narcan and improved quality of safer drugs like weed are making a difference.