I am happy for you. Good first platonic date overall.
I think your husband is right that you just need to accept his answer that he is alright. It is his responsibility to state when he is not. Or to tell you later if something did bother him. He can also say that something is alright, but later not feel like it is ok. It may be after something has happened, but that can be worked out as long as you two keep talking.
I say that you should enjoy this time and the build up of NRE. Keep doing what you have been doing (communication) and I think you are in for some good experiences.