[Tknl]

Your anecdote is in the basis correct. Very few relationships which start closed and go to open/poly survive as you do not have the required communication skills or emotional intelligence to make it work. This is usually developed over several failed relationships, similar to monogamy. I suspect relationships that start out polyamarous have a similar failure rate to nonmonogamy. Also, it is advisable to find local poly meetups to get social support and hear about what works. I've been polyamorous for around a decade and I don't date anyone that is just learning the ropes. It is too much of a risk to my existing relationships. Some of the skill sets required are covered in the book Polysecure. Trying to become poly to save your relationship is almost certainly going to fail. Do some marriage counseling first and then consider it if you have an emotionally secure base, but be aware it still likely will blow up.