Do you get a "famine" notification in the form of a red shaded corn above the next turn button? I had this in one game some time ago, and posed a similar question here. I found no way out of the negative food spiral, not with resources nor with settling a town nearby that is connected. As no one could help me, and famine as a concept was nowhere to be found in the civillopedia and wiki, I assumed it is an artifact from a mechanic that was planned at some point but not included or part of a scratched crises, and I somehow found a way to trigger it nonetheless. Seem like you are having the same problem now. It's really stupid, as you have no way to reduce the food consumption (specialists cannot be removed), and increasing the food income somehow is blocked.
As negative as this inescapable situation is right now, I still think famine crises or mechanics are absolutely necessary for the game.