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In order to spawn a fireball, you have to specify the direction. OP's direction nbt tag is invalid, which is why the fireball despawned: `direction:[0:0.0d,1:0.0d,2:0.0d]`

There is however a bug in 1.15 where fireballs disappear when spawned, only to appear about 2 or 3 seconds later.

I just messed around with it a bit further, and it appears that by using the glowing effect rather than the nbt parameter, the rendering glitch no longer occurs.

 
summon minecraft:magma_cube ~ ~ ~ {NoGravity:1b,Silent:1b,Invulnerable:1b,PersistenceRequired:1b,NoAI:1b,Size:1,ActiveEffects:[{Id:14b,Amplifier:1b,Duration:1000000,ShowParticles:0b},{Id:24b,Amplifier:1b,Duration:1000000,ShowParticles:0b}]}

If you set the motion of the armor stand in the same tick as the rotation, this bug is 100% reproducible every time:

execute store result entity @e[name=standEntity,limit=1] Rotation[0] float 0.001 run data get entity @p Rotation[0] 1000
execute store result entity @e[name=standEntity,limit=1] Rotation[1] float 0.001 run data get entity @p Rotation[1] 1000
execute store result entity @e[name=standEntity,limit=1] Motion[0] double 0.001 run data get entity @s Motion[0] 1000
execute store result entity @e[name=standEntity,limit=1] Motion[1] double 0.001 run data get entity @s Motion[1] 1000
execute store result entity @e[name=standEntity,limit=1] Motion[2] double 0.001 run data get entity @s Motion[2] 1000

If you execute this function as a moving entity, the armor stand will copy its velocity but will not visually update its own rotation. If you display hitboxes, the blue line is pointing in the correct direction.

This is still the case in 1.14.2 Can be reproduced in datapack by adding the following to an mcfunction file:

 
summon minecraft:armor_stand ~ ~ ~{CustomNameVisible:0b,Small:1b,Invulnerable:1b,Invisible:1b,PersistenceRequired:1b,DisabledSlots:4144959,ArmorItems:[{},{},{},{id:"minecraft:trident",Count:1b,tag:{CustomModelData:15670002}}],CustomName:"{\"text\":\"stand\"}",Tags:["newStand"]}
executestore result entity @e[tag=newStand,limit=1] Rotation[0] float 0.001run dataget entity @p Rotation[0] 1000
executestore result entity @e[tag=newStand,limit=1] Rotation[1] float 0.001run dataget entity @p Rotation[1] 1000
 

Run this function as the player and the summoned armor stand will not have the same rotation as the player. Reload the world and it will.

You can see this in the video I added. The hammer is placed on the head of an armor stand. When the game reloads it is rotated correctly. It is summoned using very similar commands to those above.

Can confirm for Minecraft 1.14.2 - both bow and trident damage is not tracked

^{1.14 release. Here is a screen recording of the problem with F3 open. Issue not present in previous releases. Looks terrible!}

^{The seed is -5289714038411177434}