(archery datapack) Need help changing physics and damage attributes of custom arrows

hello! i am new to making datapacks and new to working in java in general. as a little bit of practice i started by making a recipe tweak for arrows (crafted with cobble instead of flint) and a custom "gold arrow" (crafted with gold ingot instead of flint). I was able to get these custom recipes to work as well as adding a custom name (Gold Arrow) to the arrows crafted using gold, but thats as far as i got with it and I want to add some more unique behavior for the gold arrows
while i want the regular arrow to function the same as vanilla, my design idea and dream for this gold arrow is to: 
1. do less damage than regular arrows (do maybe 4 damage with a bow compared to the vanilla arrows 6)
2. fly in a straight line when shot in the direction you are aiming so it doesnt fall/have-a-downward-trajectory when shot (similar to jester arrows in terraria how they arent affected by gravity)
this is the current file structure i have for the datapack:
/
├── data/
│   └── minecraft/
│       ├── recipes/
│       │   ├── arrow.json
│       │   └── gold_arrow_recipe.json
│       └── tags/
│           └── items/
│               └── gold_arrow.json
└── pack.mcmeta
(all of the included json files are in the file sections of this post)
I understand that what im trying to do is probably very complicated especially for what im qualified to do, but i would greatly appreciate some guidance on where i can start to add the proper functions/code and file structure i need for it to behave the way im envisioning. (also if u see something that looks off about my current code or file structure please tell me because im kinda going at this blind lol)
thank you so much for reading this and i will love you forever if you can help me get on the right track with this project!