Yeah, there's a subway near me, and I can do the salad bowls (basically a sammich without bread). I already eat my subs with spicy brown mustard, and I don't care for potato chips, so there'd be almost no carbs in the meal.The standard serving size (from which their nutrition pdfs are drawn) is probably not just 1 tbsp of cheese sauce (that sounds like very little). Flour/cornstarch adds up really quick.
Might want to start packing your lunches, it makes life easier (and cheaper). Otherwise, I've found CYOA food places like Moe's and Subway to be very safe bets for variety, as you can construct several safe meals in advance and rattle them off from your notes. That avoids the issue with most restaurants where you only find 1-2 things you allow yourself to eat.
And I've already found these for snacking: Amazon product
hot pork rinds...