I'm happy to see your doing all you can to save him, but you and he may have quite a battle ahead if he does survive. Most won't and eventually fade. A sad reality in most bully breeds. Not just Olde English Bulldogges. As for his lack of weight/stamina, unlike the pups who doesn't have to work hard to overcome an affliction. He's putting all of his energy into it with little to no results.
Even though it's hard to take or understand.
Sometimes we just have to let nature take it's course. I applaud your efforts and hope it works out for you. Surgery may be your best bet. Good luck.
BIRTH DEFECTS: CLEFT PALATE WHY AND WHEN