I don't think you can really use poly to cope with your insecurities necessarily.. perhaps you need to make sure you don't fall hook line and sinker for this new love right now so you can heal and want to be sure that you don't hurt him by giving yourself some boundaries and space to see how it feels and if anyone else interesting comes along... it sounds pretty honest to me. You aren't promising anything and aren't leading him on.
What would worry me is if you say these things and then become entwined and spout of your undying love for him only and then turn around and say "actually, remember that poly thing, well, I guess I really am."
If you make sure that the poly card is on the table then you can bring it up a year from now, 10 and it will still stand. As long as you and he know that it isn't just going to go away, that you have already addressed it, but it's on hold why you and he enjoy each others company until such time as you are ready and it feels like the right time to look at poly again... go enjoy this new romance, what the hell, love is for enjoying I think.
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