That does sound like a large dose. My son is on 15mg a day and he is 5 months. If you are finding that he is better without losec I would keep him off it and try mylanta/gaviscon. Or have you tried stomach calm (brauer). Its a natual product from the chemist. It seems to help my son. If it were me I keep my little one off the losec and if stomach calm, gaviscon wasnt helping then i would introduce a smaller amount of losec again.
Good Luck. I hope your little boy gets better soon.