The ratings are based on a number system (which is hidden). Maps are kinda like Svens for capturing. They add 10, 15, or 20 points to the points assigned at capture.
That depends on your breeding goals, Lux. Personally i would geld and keep him as fancy show gelding. He won't pass the dapples on his buckskin since it's random
I used up all my items, but got some lovely catches. Lots of EEEs I still need to bravery test, but some really shiny W/WW combos. And that WWW girl even though I only used the adventure maps on boys