You may be the math whiz, but I feel confident that your husband has a firm grasp of the concept of even and odd numbers.
It isn’t the math that is the problem. He is capable of doing 1st grade math. It is deciding how to explain the math. Those are two very different things. The truth is, great mathematicians very often do not make great math teachers, and vice versa. It probably took you all of two minutes to grasp the concept of even and odd when you were your daughter’s age. Your husband may have had a harder time. Because he has had the experience of struggling to learn math, you may have less luck in teaching elementary-level math to your daughter than he will.
Besides, when I tell someone that I feel frustrated because I lack the tools I need to do that job, what I don’t want is for the person to do the job for me. I am not incompetent, I can do the job, I just want the &$#% tool! I think this issue with your husband may fall into that category.
Here’s a hint, though. If you have a local teacher’s college, see if you and/or your husband can sneak away to their library once in awhile to thumb through the professional teaching journals. That’s where clever teachers teach their clever tricks to other teachers, where common student difficulties and possible solutions are discussed, and so on…at least, that is what the Journal of Chemical Education is, which is the one I’m familiar with. If you find the right journal, it could be a great resource.
Any elementary school teachers know a journal like that for elementary-level math and science tips?