I would worm him with the ivomectrian wormer since no other seems to be available. If you can only get paste, then I'd give about half a pea size drop in his beak. If you can get cattle pour on or injectable ivomectrian , then you can apply 1/4 cc to the skin. The poo stuck to his butt is probably due to his poo consistency as well as him laying a lot. Good that he is eating and drinking. Good that he can get up with a little help. Something is making him weak, I am thinking it is a heavy worm load. You can take a stool sample to the vet and see if they will run a fecal on it to see what you may be dealing with. They shouldn't charge a lot for a fecal..... But it depends on the vet.