It sounds like you are doing all you can do for the time being. I found it REALLY important to stick to known routines and take really small steps. Routines are a comfort and making sure he is as comfortable as possible without slowing conversation to a stop is important to moving forward.
All I can suggest is staying consistent and sticking to what he knows while dropping topics and ideas and poly theory on him every now and then. That way he will know you are not engaged in a fad and will get used to it being part of life. It sounds like you are doing just that! Good luck.
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