Hi Furner,
Firstly I second everything wise andy said!
I have a friend who is going through the same type of depression, she is constantly trying to push away the people who are closest to her including her long term boyfriend. He has over and over again refused to leave her and as it is her house she won't leave it permenantly, but goes to stay with her mum for a couple of days every now and then, I am not saying that this is what you should do by the way but just like Andy says you have to let him know that you are there for him no matter what, it will take a long time for this to sink in for him, but persevere.
As for my relationship with my friend, it can be very very hard to be her friend sometimes, she tries to make me hate her by saying things that I know she doesn't mean and every now and again saying sorry and she loves me. When I call her or go to see her, very often she doesn't have anything to say so usually I end up just chattering away. Some days she just cries down the phone to me and other days she is almost her old self again.
The ups and downs of supporting someone with depression can be terrifically hard to deal with, I don't pressure her to talk about her problems mostly I try to give her something else to think about as she has a therapist who she talks to, sometimes she does want to talk to me and I let her pour her heart out, I don't try to solve her problems and just sympathise because whenever I have tried to help her in the past with suggestions as to how she can solve various problems she finds it impossible to grasp that the problems are solvable and so gets frustrated with me and angry.
You are not alone, remember that.