Truly sorry to hear about your Dad
It's just coming up to 3 years since my Dad died suddenly but I'm fortunate that at least I've still got my Mum. It's still awful though as I was so close to him and he was a great friend as well as a parent.
Hope your brother loses the obsession with material objects thing. Hopefully it's just a way of dealing with things, although I know my Mum lost out a lot due to one of her sisters doing similar when their Mum died. :/
Try not to feel too bad. From things I've heard from people in similar situations, this is quite common. I know my Grandad died shortly after everyone had left the hospital for the night.
The main thing is you were there when he knew you were and you kept supporting him

Very easy to blame yourself but do try not to.
Look after yourself.