need help desperately ?

Yes.  It's like telling your father that you have a lump on your breast and you need to see the doctor about it.  It's like telling your father that you have a terrible infection and you need to see the doctor about it.  It's like telling your father that you have severe coughing and shortness of breath and you need to see the doctor about it.....and he says you're not allowed to.  Wait.  People become ill all the time and so not facing it only makes it worse.

The American Medical Association has declared that depression is a disease and like any other disease it responds well to therapies and medications.  And like any other disease, if left untreated or under treated it can become severe and terminal.

By not getting you to your own family doctor or a licensed mental health provider, your father is GUILTY OF MEDICAL NEGLECT OF A MINOR and in all 50 states this is punishable by law.

His turning off the WIFI is not treating your depression.

He is ignorant.

That's abuse. Lookup a hotline that helps children who have been sexually abused. I'm assuming you are 17. By your question.If you are older lookup one for adults.  You have the right to be depressed any time you need to. Your feelings matter. You've done nothing wrong. Your father may still be upset your half-brother committed suicide. You admitting what happened just let your father know why he did it. He probably couldn't handle it and that may be why he acted that way towards you. But it's no excuse. You need help to get over this.1(800)252-2873. 1-800 25 abuse. It's the same number.

It obviously upset him. He just doesn't want to talk about it. It's misplaced aggression.  

if you believe you have depression you need to practice (CBT) or cognetive behavioral therapy and take your medications on time like you should

It might not be abuse. If your half-brother was your father's son, think what the whole experience will have done to your father. He has seen a child who he no doubt cared about go completely off the rails, inflict huge damage on the family, and then kill himself. That's not an easy thing to deal with and he's probably finding it hard to come to terms with. Even if your father was out of order in how he spoke and reacted to you, there probably are reasons. Hard though it may be, the best way to respond to your father may be with patience, sympathy and forgiveness.

I'm so sorry for all this. But there is hope. These articles explain. You'll be ok.

https://www.jw.org/en/bible-teachings/teenagers/as...

https://www.jw.org/finder?docid=102001603&prefer=l...

Seek professional help.  If you can't, then talk to a school counselor about this. They can address this 

it could be emotional abuse, maybe you should tell cps about it

Right now, you are letting what happened to you control you.

You will become a victor when you learn to control it.

It's not the best way for dad to respond and I'm not sure what is going to be gained from it.  However, being blunt with you and not allowing wifi is not abuse.