I think you're looking for the wrong signs. Gay guys don't want to play with girl toys or girl clothes. They want to look at handsome men instead of beautiful women.
Straight little boys will gawk at beautiful women or embarrass you by trying to touch or look up the skirt of women or female mannequins, or will even say that pinup girl posters make their penises long. *shakes head, remembering that conversation in Walmart*
And don't say it wouldn't matter to "either of us" - it clearly is driving your husband up the wall to think of the possibility that his son is gay.
It's hard to tell at this point. Sweet loving boys who aren't aggressive is no sign that they are gay. And if they are gay, they're still your children and created that way, and still need your love and support. More than straight guys.
Many boys are sensitive, and don't have to be hitting someone or bullying others in order to be a true boy. I am grateful that all boys aren't like that. What I find is that most parents would rather have a happy easy going child around their children, and not a meany, who only worries about himself. If he likes sports, and cars, good for him. My child wishes that more people would understand Nascar, so that he could have someone his age to talk to about it!!
Good Luck, don't worry, and tell your husband to grow up!!
If your son was gay, he would be able to pick up on the non-acceptance his father is displaying, despite all the 'it wouldn't matter to either of us as we love him more than life.' That isn't fooling anyone! You need to tell your husband to cut out all the comments to you about this, and all his subtle manipulation of his son. It is going to confuse your son and won't help 'cure' him if he is gay and if he isn't gay it is certainly going to upset him to feel that his father has miscast him in a role he doesn't understand.
You are right, he is just a little boy and there is no reason for your husband to crush his innocence and knock the joy of living out of him. The world will do that soon enough.