Most recipes in book are for 2, sometimes 4 or more. I understand …”calorie counts are for one portion”. Does this mean I have to cook extra food that I cannot eat OR that I should try to halve the amount of ingredients?

Try halving it if it is possible, otherwise put a portion away for another day, maybe freeze it then you have less work to do with a ready meal. If it is for 4 then again make half and save some.