I haven't had a chance to read other peoples responses... so if there are repeats then I apologize.
Having read your post there were a few things that came to mind. It sounds like he is a bit in NRE over the chance of his freedom, just as he was in NRE when he told you you are the only one etc etc..... it's not that he was bullshitting, just that he felt that strongly in the moment. Perhaps nothing has changed for him, he is just adding to that love he has for you.
I can also imagine that he is thorough when he feel he should date four women... he is finding the one that is the most suitable and that takes time and some investment... I would check with him on that. I dated upwards of 20 guys before finding Mono... it was a lot of work and effort, but now I have him and my other loves and there is no need to date anyone else...
I would suggest that he NOT sleep with any of them, but just see if they are worth his time and he is worth theirs. Sex complicates and causes bullshit that is not the whole point of poly. It depends what you work out, but make sure it is all very clear before he ventures out. It sounds like you have some work to do on communicating that.
In fact it sounds like he needs to slow down and catch you up. Also catch up to what you are feeling. It's not okay for him to barrel forward demanding his rights to freedom and leave you in the dust.
If he isn't liking how you are behaving then make sure he knows it is because he is not paying attention to you and your needs. If you are jealous, clingy, whiny, then there is a reason and it's not okay to just ignore that and roll his eyes and move forward... he needs to slow down by the sound of it, take a breath and remind himself of his connection to you. He needs to remind himself that you have a connection and that that is the most important thing.
that's what I think... sorry this was rushed, more later possibly.
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