The quickest way to destroy your relationship is to act possessively and jealously, it breeds mistrust in a partnership between two people, as really what you're saying is that you don't trust him. You don't trust your friends, and you don't trust the two together, many people find that kind of attitude towards them unacceptable, especially if they're totally faithful, they may get in a really negative thought pattern like "Why doesn't she trust me, is it because she knows that in the same situation she wouldn't be faithful?"
You say "yay" your friend is no longer friends with him anymore, but why is that a win? Obviously it hasn't solved the problem because other friends of yours and his will be friends with him and may even flirt with him so it will recur. Evidently the problem is with you, and no amount of defriending will solve it. What if next time it's not your friend, but his? What if it's his attractive boss or a friend's sister? You wont have any control over the situation and because you're masking your feelings not dealing with them you'll end have no option but to deal with it irrationally.
If you read enough stories on here, then you'll see that the one thing a successful LDR needs more than a in-person relationship is trust. Your guy will be awake for hours when you're asleep, he'll go to bars, he'll go to clubs, he'll go out for coffee, if you can't trust him 100% then those feelings you have will eat at you, and they wont be solved by being physically together which is what so many people on here seem to think.
So, what to do? One, you need to recognize that this is a problem with you not him or your friends, stop trying to make the issue go away and try and deal with it.
Confront why it upsets you? Do you really think he'll leave you for some chick on Facebook? If so why? Is it a self esteem issue, if so - work on that! your GED is a good step, but also just reacting positively to yourself is a good start. Celebrate that you're trying to fix your educational situation, that you're being brave and traveling. All of that stuff. If you see him talking to a girl, think to yourself "yeah she's pretty and cool, but so am I, and he loves X about me and that wont change"
Discuss these changes with your partner, be really calm and say "hey I get really jealous when you talk to these girls, I know I shouldn't but I do, I'm trying to get over it", and really try and get yourself into a better thought pattern, don't try and limit his friends or his life, it wont help you or him or your relationship in the long run.