I wouldn't read anything negative into it since you said in school your were plain and now you are hot he may have been attracted to you and didn't want to let himself feel that way because he is married and he may have thought if he started staring at you he couldn't stop and out of respect for his wife he didn't want to make eye contact it's okay that he found you attractive but as long as he doesn't touch or it doesn't go any further than that. I would contact the wife you two can be friends without it being awkward and maybe if you start talking to him first he will feel more comfortable about making eye contact.
I really don't see where he would interfere with his wife and you being friends trying calling and asking her to lunch one day and take it from there it will probably take some time for him to get use to the way you look now seeing it is such a drastic change from High School. Just give him some time to get over the fact that he let such a hot woman go he may be kicking himself for not staying with you but you both have moved on you have to show him just that, tell him that was the past and you would like move on to the future and maybe him and your husband could become friends also.
After he gets over the initial shock things will get better I think he just needs some time maybe invite them over a couple more times for dinner and you initiate a conversation with him and this will help him feel more comfortable around you now. He will see that though your looks have changed your personality did not.