Make a Bossbar

-bossbar add bossbar1 "test"
-bossbar set minecraft:bossbar1 players @a
-bossbar set minecraft:bossbar1 color red
-bossbar set minecraft:bossbar1 style notched_20
now the part with exact details
get a command block (/give @p minecraft:command_block)
set it to
-summon iron_golem ~ ~ ~ {Health:10000f,Attributes:[

,{Name:generic.attackDamage,Base:10000}]}
and summon it PRIOR the following
place another command block and set it to repeat
Enter: 
-execute as @e[tag=test] store result bossbar bossbar1 value run data get entity @s Health
and set another command block on impuls running the following
-execute as @e[tag=test] store result bossbar bossbar1 max run data get entity @s Attributes[0].Base

Thus the Bossbar at the top will display the exact value of 1024 for whatever reason...
The Maximum value is locked on 10000 as it should, but the current health value is capped at 1024 for no reason, you can check this via
-/bossbar get minecraft:bossbar1 value 
Seriously this should not be the case...

Double report, this golem has 10000 Attack Damage but doesnt oneshot anything, this should also not be the case

Additional things

-Spawners lose their given stats when placed, I made a custom sheep spawner and when I placed it down it became a pig spawner
-A Zombie with 100 Health dies as fast as a Zombie with 20 Health when standing on Magma Blocks / in fire... Is this wanted? Its weird to me
-Custom Tags in .Json files get accepted but have no output in the game for example in custom crafting recipes... Theres something wrong there