Without the ability to message someone on OKC, what possible point could there be in the site's existence. There are other poly-friendly dating sites and I can post a list here if you're interested, although they're probably not frequented as much as OKC. Although as I said, no matter how popular OKC is, what's the point if members can't message each other?
It sounds like your confidence and ability have extended somewhat in recent months; I hope you can find a way to test yourself. There is of course always getting out there and meeting people in real life (meatspace). But let me know if you want that list of alternative dating sites.