I'd keep up with the milk for a while longer - if he's eaten too much creep today, he'll do so even more if you stop his milk

But take care to not give too much milk in a sitting, and creep ditto. In theory it shouldn't matter if he has creep immediately after milk, as they go into different stomachs, but I generally leave them for an hour or so after milk before giving any quantity of creep. (A few pellets won't hurt.)
As to tonight, I'd be inclined to include some natural yoghurt in his milk feed, and give him maybe half what you'd normally give.
Would he eat straw instead of hay? Some people think the longer stems of hay can cause issues, and nice barley or oat straw should be safe.