God this sounds awful, what a crisis. I'm so sorry to hear of your brother, and your father. It must be so terribly stressful for all of you.
My DB was sectioned for psychosis, with delusional and violent symptoms. We knew something wasn't right for a while, he lost his job and had declined before that. It's a relief to get a diagnosis but also awful that it reached that point, you have my sympathies.
DB was very confused when we saw him. The first time we spoke properly he said he didn't know why he was there. I really didn't know what to say either.
I would probably not visit for a little while OP. I only went a couple of times and stayed for an hour or so, taking a game, talking about shared interests, things you both find funny. They can be awful places, DM visited, a patient opened the door and said DB had died!
Taking medication is the key thing to help stabilise his symptoms. Also having insight into how Bipolar affects him. If you can, read up about Bipolar as it can help to have empathy/understanding. Doing WRAP planning is really good - it covers signs of a crisis and what to do etc: mentalhealthrecovery.com/
Also have a look at the current NICE guidelines.
Is the living situation with your DF? Can DF have him home or does DB need to go into more semi-independent accommodation.
Family members / siblings experience FOG (fear obligation guilt), look after yourself and put your needs first. For siblings:
www.rethink.org/carers-family-friends/brothers-and-sisters-siblings-network