How I got the Armor Points, Damage, And Mob/Name of mob to display on the bossbar, is through execute. I executed at the player as one MOB nearest, then ran bossbar set name. I set the name with the first line of text being Selector @s, Second being the separator, Third being the Damage Count, and the final being Armor Points. I used @s because wildcards(*) don't work with mobs.

EDIT: I changed the way it works. Above was what used to work (except the selectors). Instead I executed as the player then used a selector for finding the nearest entity with AI.

Now as for the rest of the commands, they're pretty easy.

While you're here, I may as well address: Unfortunately, just like mods, some datapacks are non-compatible with others. So check your datapack's compatibility with others first before releasing. This is why I used @s rather than separate mob bars.