There might be a separate file for the lilypad used for the inventory, the one you altered was in model/blocks but try to see if there's one in model/items
If you get full control over the resource pack that means that you can change up the resolution, do whatever you want with it. Even changing up the style of it, although that is not something I think people will do.
I'm creatively exhausted on the project and for me to put a lot of effort into it, then ending up with practically the same resource pack as my other one is not something I want.
I have been trying to keep the resource pack in an 8x8 resolution, after a while making textures in that resolution became difficult. I think it all would look better in a higher resolution, but I've already got a similar resource pack that does that.
At first I wanted to abandon and delete the resource pack but then I thought that maybe someone else could do the things with the resource pack that I couldn't.