Similarly, I'd love to know how many calories in what I spill.
Part of my disability is a serious case of the dropsies, I probably drop/spill about 150 calories every day, but don't know for sure. I just chalk it all up to an estimate and figure that it doesn't matter too much, it's never
that accurate. The only way to be sure of the calories in your exact personal meal and know that the ingredients added in manufacturing (e.g. bread, cereal) it were smoothly averaged out into your personal serving is to set fire to it in a calorimeter. Since you don't do that...
Is there a reason you routinely put on too much milk? Since you are making lifestyle changes just now anyway why not just put on a bit less each day, or if you are worried it might end up too dry put on whatever amount, say 4oz on the cereal and keep 2oz in a jug so you can put it on if required. Then you can put the excess back rather than throw it away. Add up how much you pour away each year and think of the impact of all those cows, all those diesel miles bringing it to the store for you to buy and then chuck out, it might motivate you to just use what you need.