The first few days (maybe even a week or two) after that decision is made, can be hard. Everything is in flux. The example you gave of sitting down to eat and it not feeling "right" anymore is a really good example of that.
Everything that was normal in your home life is now not normal (good and bad). Those are tough changes absolutely.
But in many ways it is like any big change, change of job, new child, moving to a new place, your new life will become normal, but it takes time. Of course this is a sad decision so it makes it even harder.
But, it will change and you will be ok and you won't always feel sad about it.
His reaction is obviously cool as you mentioned, he just carries on. That just goes to show that he is lacking some of those really important attributes that add to a relationship, compassion, connected-ness, which, of course is why your relationship is where it is.
It will get better and in pretty short order, just try to hold on to that when you are feeling down. There is an upside to this, there is a freedom, you just haven't really experienced it yet.