Welcome Bigpolyfamily, wow, that sounds like a very complex situation but I hope that it all works out. I think it is possible if you all enjoy each other for what you have to give and stop thinking of each other in a competitive light. At present there must be a lot of NRE going on, but don't let that make you neglect your other partners. Also, right now some of your language (please don't be offended) is very much in the realm of NRE drunkeness, it is like crack maaaaaaan, it makes you believe stuff that is probably not true.
Please try to relax and enjoy the relationship for what it is, keep up the communication between your partners and metamours and try to wait until the NRE is over before making any big life changes.