Not being honest with your partner(s) is't called polyfuckery, its called being a douche. Polyfuckery is basically having multiple sexual relationships. If I understand this correctly, he terminated other relationships to give you your year of monogamy, or "foundation building" and now you are worried he will rekindle those relationships. To be honest, if I have understood correctly, I'd be nervous too. He previously treated people like disposable commodities and he might do the same to you.
If that isn't the case, then you simply have trust issues that won't be conducive to healthy poly relationships. This might be because he has given you reason to mistrust him or because you just jar trust issues. Either way, they will fuck things up, long term. You need to establish whether he is trustworhy and then make your decisions from there.