I take it in the middle of my breakfast and the same with my evening meal. I'm fortunate in not having suffered any of the side-effects but I know there are many more who have.
If your hubby's taking his 1,500mg of Metformin in 500mg tablets, might I suggest he takes one tablet during each of 3 meals, rather than 2, during the day, e.g. breakfast, lunch and evening meal? That would even-out the dose and I'd have thought it should reduce the potential for side-effects.