About mouse guard

Questions, firstly, what does +1s mean? I still do not understand how weapons benefit the player using them. Secondly, wouldn’t all players be better off with a low Nature score? what are the benefits of a high nature score? And finally, how can we homebrew other creatures like hares and hawks to be playable critters? Also, how can we add magic? I just added Arcana to either replace one starting skill or it can be learned.