Hi, and welcome to the amazing World of the module development!

That questions can be easilly answered:
The horses, arrows and spears are items, to edit it you should download and install the Module System (there are a lot of tutorials about this), when you are ready locate
module_items.py file and modify the item flags of each object:
For example:

To change the damage that causes a horse, edit the following flag:
horse_charge(14)

To change the damage that causes a
bow/pistol/crossbow, edit the following flag:
thrust_damage(41 ,pierce)
(you can also change the type of damage)

The same process for every item, you just should find the correct flag... its very easy...
PD: Do not use notepad to open the .py files use
Notepad++ or
Notepad2. Greetings from Spain
