Shannon, hugs! I hear you, this is getting really tough! I think you really really need more foods for your sanity/stress/supply since they are all linked. He's probably just putting on some good amounts of weight and drinking you dry
Remember naps are always lousy during a growth spurt, they are more interesting in waking to eat.
Here's an idea: forge ahead and keep eating one food for consecutive days, without stopping that food until you are 100% sure that it is a reaction. If you stop after only one day of the food you can never be too sure, and remember that our bubs have off days anyway, you need to look for patterns of consecutuve bad days, with all symptoms amplified to be sure that it is a food intolerance reaction.
What is it other than bad naps and his frequent feeding that is holding you off from adding a new food? Is he mega relfuxy of just off? If he is just a "bit off" I would forge ahead.
I am nervous about oatmeal for you because of the small gluten content. To be honest I would try potato again and keep going for a few days on it. Otherwise you willbe forever scared of potato. You said there were other factors that could have caused the reaction. Or else Quinoa grain, or else lamb or veal.
Going on a "low" diet is a good idea, you will add at least 20 foods all at once that way.
hugs hugs hang in there....