I don't have much experience with this but this is what I would do.
First address any husbandry issues that may be present (You're temperatures sound fine as long as they are being accurately measured. Make sure he has places to hide so he can feel secure) .
Leave him alone for two weeks with minimal interaction (water changes,cleaning), then try and feed him again. When you feed him feed him a meal smaller than you would normally feed. If he regurges or vomits the next meal, seek the attention of a qualified vet in your area.
I'm not totally sure what you mean about the breathing. When snakes are stressed/ feeling vulnerable, respiration seems to increase. You will most likely notice this if you lift the hide off of a sleeping snake and startle it. If there is wheezing or whistling present, or maybe a slight popping sound, don't hesitate to get him to a vet. Especially if you see any mucous / bubbles around the nose or mouth area.
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