I would agree that the IQ testing is probably not a completely accurate picture of his abilities. In addition to the question of learning disabilities, his experience of English may be different from other children growing up in this country, as he is hearing multiple languages at home, and English from non-native speakers. It is likely that there are verbal concepts that he understands, for which he has made up his own terms, because he has not had as much exposure to the standard English terms. Or words that he knows only from reading, which he wouldn't recognize if said out loud.
I do think also that the parenting relationship between you and your son is more important than the educational or giftedness questions. You have a lot to offer to him. Whatever his level of intelligence, you are still his mother, who loves him, takes care of him, comforts him when he is sad, and is there to teach him about life and how to be a good human being. You don't have to understand all of his ideas, or be able to answer all of his questions, but you can still show an interest in his thoughts by asking him to explain them, and writing down his questions to look up later. You can also demonstrate to him that there are different kinds of skills, and different contributions people make to a family. Even when you do household activities, you can explain what you are doing (also a way of showing him what explaining something looks like)--such as how and why one sorts laundry by fabric or color, how one selects or cuts vegetables to prepare a meal, the thought process that might have gone into decorating a room.
I think it is very good that you have tried to enter into his interests, and feed his desire for knowledge in those areas, but it might provide some balance for him to see that you already have large stores of knowledge in some other areas, that might not have been particular interests to him, but are very useful for life.
Finally, it may be worthwhile for you and your husband to sit down periodically, when your son is out of the house, or is asleep, to talk about how you feel, your concerns about meeting his needs intellectually, his attitude toward each of his parents, and how best to help him grow both academically, and as a respectful and compassionate human being. There are always challenges in parenting, and it is even harder when work schedules mean you are parenting separately much of the time.
