Is he able to stand?
How long since the fight?
You mentioned bruising under the wing (?) is he having any difficulty breathing?
I'm sorry he's not getting better. Sometimes when a bird has been in a fight, they can lose some confidence for a short period of time.
Since he's not improving with supportive care, then he may have suffered more injury than you initially suspected or he may also have something else going on. Sometimes stress/trauma can cause an underlying illness to present.
Check him over again really well, for more bruising, injury, etc. A lot of times all you can do is work on hydration, then nutrition. Green poop can also be from a number of things from not eating to infection to worms.