Thanks for writing to Just Answer.
You will not like this answer, I'm afraid. There are a lot of red flags in what you wrote that should warn you away from trying to pursue a relationship with this man.
1.He is married, with a child
2. He is moody
3. He is senior to you--and this is important in a tight job market.
The reason he isn't treating you the same is because he was attracted to you at one point. The other ladies in the office aren't a threat to him--whereas you and he have exchanged personal information, and at least mentally toyed with the idea of an attraction.
If he has decided to remain faithful in his marriage, he "can't afford" to be nice to you anymore. Looking away , raised eyebrows and leaving the room, etc. is very likely making it worse, as those are the actions of a jilted lover. What are the other people in the office thinking when you ignore a senior staff person, or walk out of the room when he arrives? He can be nice to the older married lady because she is safe.
In this economy and tight job market it is just too dangerous to have romantic entanglements at work (or the appearance of a romance). Try to stop sending him signals by behaving differently when he comes around. Go back to being professional, and don't try to bring up personal matters with him. Let this "thing" between you go...Take comfort in the fact that he found you attractive, but remember he is married, and higher up the employment chain than you.
Make more of an effort to find men to date outside of your work world, and the memory of this email fling will fade. It is always the woman who pays the price for situations like this at work. It's not worth it for a married man.
I know this isn't what you wanted to hear, but it is what I believe to be true based on both my counseling and life experience.
I wish you all the best in finding someone new to distract you from this whole thing...