I play it with my friends on the weekends sometimes.
1. The ratings on the character select screen only tell half the story. The Running, I know for sure, affects how fast a batting character runs after hitting the ball. Fielding, i'm guessing, is how fast they run in the outfield while not in possession of a ball, but they run FASTER once they do have the ball; and their default throwing ability. Throwing in the field is based on a "buddy" system. All the characters are set to be coorperative with a selected group of characters. If the thrower and reciever aren't buddies, the throw is slow and weak. If they are buddies, the throw is OBVIOUSlY fast. Buddy pairs can be spotted when a Music Note Icon pops up by them when the ball is thrown, which means you have to discover the pairings yourself.
2. X tells the runners to go to the previous base, Y tells the runners to advance to the next one.
3. Pitching power/quality is affected by how long you hold A, and when you let go (like a simple, invisible Mario Golf swing meter). The more power pitches that are tossed, the sooner your pitcher will want to retire.
4. Standing is a very basic action, not a lot happens until the ball is in motion. Every [type of] character has unique animations for swinging, strike-outs, pitching, running, and stepping to the plate. Some characters have specific special catching/reaching abilities in the outfield by pressing A. (Yoshi's tongue, wall jumps, paratroopa flying high, etc) Special pitches and swings are performed by holding R trigger then holding A.
Menus are simply menus, and the interface isn't very animated.