[souffle]

He sounds to be on his way to bridge I am sorry to say. I would cover him up and let him pass peacefully in his own time. Tell him it is OK to go now. If he is still gasping he has not quite crossed yet but will be deeply unconcious so feeling no pain so don't fret.
The blood from his vents sound like he has a prolapsed bowel which he would not be able to survive.
I'm so sorry. Talk gently and check on him hourly.
Once he passes his body will go stiff and then after about 12hrs soft again. His soul will have gone over the bridge by then and you can lay him to rest.
I hope his path is gentle. Stay strong and walk a little way with him.