Aww bless you seem really sweet, and seem to have a good heart. Your husband is foolish to have done what he has done.
And foolish is the word. Are you sure it is definately only emotional cheating and nothing more? I mean the girl on skype actually said she misses him and he felt compelled to answer - that is a big problem right there to be honest. What if she eventually told him I want to have sex with you in person? Can you trust him that much to say he would not be that weak?
And the girl he has known for 16 years, to have anything remotely sexual whether physical or emotional with her should be out the question completely or it becomes a major issue. What has gone on there?
He doesn't want to admit anything freely you say, then how on earth does he feel you will be able to trust him?
You seem to nice for your own good unfortunately, don't be a pushover for him as we all know if someone gets away with it once then why not a second time. We all know what troubles relationships can go through the longer it progresses especially sexually and ultimately it relies on the couples ability to communicate each others frustrations and problems on a regular basis and a matual respect on both sides to be able to work hard at rendering them.......
You state that you drifted apart over the years and understandably it became second nature.
Your husband has sexual needs just like you do. If you guys haven't had intercourse in a long time? them that spells trouble. What your husband did was wrong but the only salvage point you need to make sure of is that it was only emotional.
Have a good hard chat with him and lay down the ground rules. If he steps beyond his mark and you catch him doing that nonsense again make sure he knows what to expect! At the same time, you both need to talk to each other on how to improve the relationship and what each others wants are.
10 years is a long time, I wish you guys the very best.