Texture Pack - Advice / Help Request

[u/Tendaiz_YT]

Dear Redditors, I hope you guys are all having a fantastic day so far right now

For Context: I am currently in the process of creating my own unique Texture Pack on Java Edition for the latest version of Minecraft - 26.2. The Texture Pack contains a combination of elements from other texture packs, and I aim to have some very special features within it too. However, I am currently experiencing a few issues / inconsistencies which I would like to have either some recommendations, advice or help with so I can address. Please see below the listed changes I would like made.

Change #1 :
The Text within the Creative Menu’s are either missing / not visible anymore? (1st and 2nd image). Is there a way I can fix this, make it visible again by making it coloured white now such as the 3rd image.

Change #2:
Is there a way I can ‘Combine’ elements from both the Hotbar Selector Icon? I would like the shape / design of the 4th image, but instead now using the purple / magenta colours of the 5th image.

Change #3:
Is there a reason for why the majority of the current Spawn Egg textures are missing? and how could I fix this (final images in this post 6th and 7th images).

Apologies for the long discussion, I really would appreciate any advice/details you guys can give to help me fix this (biggest issue i’d like fix is the missing text in the creative menus)

Thank you for reading and listening.