based on what Raymond says at the trial, do you believe he did all he could to help Meursault?

Yes, I believe he did. The two have a friendship that's really not (if that makes sense). Raymond initially befriends Meursault in order to use him for his own benefit, but even so, he is loyal to Meusault at the trial and believes himself to be somewhat responsible for supplying him with the gun. Nonetheless, Meursault was unwilling to help himself at the trial. I think Raymond did all he could.....