K.C.
A.,
This is not normal behavior at this age. I do think it has something to do with your husband's absence. It may be that your son is trying to parent you and give you what he perceives is missing in your relationship with your husband. If something makes you uncomfortable, you need to say that. "In public" is irrelevant. Tell him it makes you uncomfortable all of the time and that he is to stop it. Also remind him that you love him as a SON. Dad is your boyfriend love and he is your son love and it is different. You can tell him that you hope he has a girlfriend when he is 18 with whom he can be so loving but that this behavior with you is inappropriate and must stop. Kids have fantastic imaginations, do not fuel his. I remember trying to kiss my dad on the lips and being told NO in no uncertain way. I still knew I was loved, it didn't feel like rejection. Just appropriate and inappropriate.
Hope this helps. The Oedipus complex is over by 6, by the way. 10 is an age to start pulling away from mom.
Good luck!
K.