Hi, Phy, and welcome!
You've been given 2 loads of good advice. I hope mine also helps.
a) This is new to you. 4 years ago (3 1/2?), your skype friend lets you know that he's interested. You reject him in clear terms, but are mad at yourself for having that same interest. 2 weeks ago you're both honest with each other about it, admit that the attraction is mutual. It took you 3 years to come to terms with your own desires. How can you expect your husband to be quicker to accept the "rightness" of desires that aren't his?
BUT b) [And this is what I consider even more important.] You haven't yet talked to your husband. You're worrying, fearing that he'll get really upset about all this. How do you know? OK, you know your husband better than any of us, you have a feeling about how he would react based on your experience of him. But he, himself, mentioned (joking) the possibility of a 3-some. Do you know the expression: "Many a true word is spoken in jest"?
c) Imagine - just imagine - that your husband has thought about opening up your relationship... but doesn't bring up the subject with you because he fears how you might react!
d) How well does your husband know you? When you all met at New Year's Eve (and have the 2 of them met since then?) do you think that your husband might have guessed that there were strong feelings there?
e) You write "He knows how important my friend is for me and how much he means to me." I honestly can't imagine ANY man knowing this without considering the possibility of an added sexual attraction being there.
f) Some husbands get wildly jealous about their wives' strictly and obviously only platonic friendships with other men.
g) Your husband - from your account - is maturer than that. He might be (at least) understanding of the existing of a sexual interest.
h) Be honest with your husband. Tell him how you feel. Don't expect him to jump up, clap hands, and shout: "Great!" Give him time to get used to the idea. (Didn't it take you 3 years?) He might surprise you by taking less time...
i) If you really don't want to lose your husband, if he really is important to you, don't lie to him... and don't put yourself and your other friend in a position where you might do something that you feel you'll need to hide from your husband.
If I can't dance, I want no part in your Revolution.
- Emma Goldman Anarchist and Polyamorous par excellenceThe person who says something is impossible should not interrupt the person who is doing it.
- old Chinese proverbAnd the day came when the risk to remain tight in a bud was more painful than the risk it took to blossom.
~ Anais NinI'd rather have a broken heart / Than have a heart of stone.