Am I justified to be upset over this? How to deal with it? Does he still have feelings for his ex?

I do not think you are over reacting. I think all men have some feelings for their ex's unless they are cold hearted *******. I still care about my ex wifes welfare even though I have been re-married for over a year. No one can say but you what your man is capable of. Some guys handle boundaries very well and others easily cross over them. Just keep your wits about you and see how it plays out.