Ulcer that are persistent always IME have an issue driving them I hope something can be done for the foot issue when you get a diagnoses .
Good luck with it all.
Hopefully the feet are what has been causing the ulcers.
However what do you want todo next? How much money do you have to spend on him? I don't think taking him if gastroguard Atm would be q good idea at all, but if you have to pay for it yourself ask the vet for one of the cheaper alternatives listed above