I'm sorry for your loss...
I think it's quite normal, There are people who mourn for their beloved even after decades.
About the fb posts, what you're doing is normal, you're trying to contact him though he is no more, just like loved ones go to the cementery to place flowers, give messages, to remind themselves of special moments, to talk... am I right? I think I am.
It is unimaginably painful when you realize that someone you love is no more.
But as time goes on, we have to build up strength all by ourselves to overcome the grieving or else one day it may eat us.
To overcome this, try to look at the basic facts and accept them.
1. Your friend passed away, and never going to come back, no matter how hard you cry or how emotional you get...this is true.
2. Don't look for If's (If I was there, If there was a hospital nearby, if he had taken a leave, etc.,.) whatever happened is happened, no one can go to past and change its course & you have to realize that there is no point in arguing with 'If's' it only causes more pain to you.
3. As long as you have memories of your friend, he's still alive, alive in you.
4. Your friend doesn't want you to cry for him, all he wishes is for you to be happy.
Though it's painful, it is also inevitable...accept it and move on...
The best suggestion I could give you is...go to service
-serve people who are in need, who need a helping hand just to survive, do some volunteer work for the destitute or for an orphanage, etc.
-plant a tree and give it your friend's name, look at the tree as it grows so is your relation with your friend grows too...
-Save an animal from slaughter or concentration camps, tell the animal that it's your friend who save it not you even though the animal doesn't understand what you're saying.
Serve everything under the name of your friend...
If someone asks you why you're doing this or what motivates you to do this....point them to your friend.
If someone thanks you, give all the credit to your friend and take none for yourself.
it makes you a lot happier both physically and mentally.
If money or some other thing is stopping you from doing volunteer work, don't worry, do as much as you physically or financially can go...
"Whatever you do will be insignificant, but it is very important that you do it" -M.K.Gandhi