polyamories are really complicated and can very easily end in ruin, speaking from personal experience. tread carefully
I'd say it's not really polyamory if they're not looking for romantic attachment out of the third. I don't know if I would even call it an open relationship, since they're only going with this singular third person.
Anyways, it depends on the individual. Some people can have love with a person without developing emotional/romantic attachment to them, some can't. If either of you are the type who can't, then it's best to avoid it, if romantic involvement isn't what you want.
If you asked me a few years ago, I would say "no way, relationships should stay between you two" but since then I've actually met a lot of people and seen how increasingly common these non-traditional, non-monogamous relationship structures are. I have many friends in long lasting open relationships and it works completely fine for them. It's just a matter of it it works for you
Not worth it. 9 times out 10 this will result in infidelity or relationship ending issues.
Can you provide any source for this statistic you're citing?
