I'm not sure calling the collapse of the AMOC a "questionable idea regarding a hypothetical event that's not even remotely shown itself in actual measurement" maps with reality. Scientists have been dumping data to models and for a few years this possiblity has gone from unlikely to "it could happen within the next 5 to 10 years".

Look at Canada or Russia and you see what will happen. It will be too cold to grow most crops as well as today, but it wont be another ice age, humans will still survive in the area albeit you might need a bit more energy to heat your homes and food will be blander or rely on imports (food diversity coming from imports wouldn't be very different from today though...).

Climate change ensures no ice age will happen again for millions of years, the ice age happened since earth was extremely low on Co2 it wont happen at the rates we have now.