Wow, all of you have a lot going on. I suppose the best thing is to be there for your friend and hopefully he can be there for you. Mutually support each other and lean on each other. Also, do you have other friends you can reach out to or that can reach out to you? It is good to have more than one friend to lean on. Also, we have to understand that people can love us and still let us down sometimes because we are all human.
Also, is there a trusted adult you can confide in for help?
Depression is a beast that can feel overbearing, and it takes a battle to overcome. Sometimes you get tired of fighting the battle but you can't give up.
Are there activities or hobbies you can get involved in? I know it helps me to get out and do stuff. Problem is, depression can make it hard to motivate yourself to do things.
I know it is hard when you are leaning on someone for help and that person is so burdened by someone else's trouble that they can't be that helpful to you. Best of wishes. You are in my thoughts and prayers.

