I lost a very good mate down in Bournemouth to suicide a few years back and I still beat myself up over it as the signs were there and I ignored them, such a genuine bloke who helped everyone, but nobody was there for him in his hour of need
Try being a bit easier on yourself Cat. You can't be all things to your friends. It's also worth remembering that he made a choice, tough as that may sound. I'm sincerely sorry for your loss and full of admiration for your compassion.