I know this might be too much, but can somebody help me with some of it? :(

fur color: i would say that fur color probably does not matter much. it may play a part if were talking about how well they may blend in, but that would depend on their environment. overall i would say this one is probably not that effective.

heat tolerance: i think that a wombat with higher heat tolerance is definitely going to have some advantage over one that has lower tolerance. their environment may change, and ones with higher tolerance will be able to adapt much better than one with a low tolerance.

birth coat: i think this may have some importance. because an animals fur is generally quite useful for many things. so i think a wombat with fur, may have more advantages than one that doesnt have any.

running speed: i think a wombat who is able to run faster has a great advantage over one that is slow. if they ever need a quicm getaway to avoid a predator, a fast running wombat, is going to benefit much better than one that is slow.

ear size: a larger ear will travel slightly more sound into the ear canal, but at the end of the day it is not that much of a difference if you compare it to a smaller ear. so ear size would probably not matter.

i hope that i could be of some help to you :)