I have no experience in repair of a blown head, but provide observations:
1) The cracks may be the main issue you have. If it were me, I would get an entire new head.
2) Assume when you say coolant leak, you mean losing coolant, but nothing external. I am also not sure of the exact process of measuring the "flatness" of the head, but have a hard time believing that if you have those cracks, that the head is not warped and thus pulled away from the gasket allowing coolant into the cylinders.
3) I also notice that the back 2 cylinders are covered with carbon and the front 2 are not. Not sure whether the coolant would provide a detergent to wash the front 2 or poor burning to "muck" up the back 2, but you obviously have very different firing between the 2 pairs of cylinders.
I would take to a high end machine shop that does heads and start asking questions.
13 S5 Manual
03 1.8t sport Quattro with 115K
02 sport quattro with 205K; (killed by a 4x4)