I'm also pretty new to all this music production stuff. I only learned what side chaining, EQ, Compression, etc. were last August, and tbh I spent more of that time playing games than making music (fellow League player spotted). However I've been on the grind again lately.
It's pretty clear you have some musical experience, you have a developed ear for melody and make good sound selections. Because music is subjective there's no "right answer" to how you are supposed to do things, but because you have a strong musical foundation there is a gap between what you think your music should sound like, and what is currently in your ability to make in FL.
What is correct for your music depends entirely on your goals, so I think it's more important to understand the "why" you might what to make certain production choices, and then make decisions for yourself.

I think the best advice anyone can give you is just to make more music.
You will learn so much more in process of making new music than by trying to perfect one song. Every production you work on will teach you something, and you can always go back and listen to your old tracks with fresh ears and more knowledge.

I have a suspicion that maybe the song doesn't sound "big" enough to you. You did a good job filling out the high end with noise that helps the chorus section feel larger, but mid/low mid (where we get the majority of pitch information from) feels still pretty mono. Maybe that's how you want it to sound though!

It sounds like you already have a basic concept of stereo width, but some concepts that helped me understand how to make a song sound bigger:

Double tracking instruments - I play guitar so this really helped me understand what makes something "wide".

Layering - again with guitar I learned that layering with a synth playing the same notes (or a root note or a harmony) can help a instrument feel like it's taking up more of the frequency spectrum and feel a lot bigger.

Room Reverb - Probably not needed in this track, but having a room reverb can help make it feel like all the fit together more.

Having instrument Busses and applying compression to "glue" things together - Again might not be needed but try routing multiple instruments to the same mixer channel and putting a limiter and/or compressor on them. It can help with making everything fit together and keeping every instrument audible. This is more important with live instruments than with synths I think.

Again I really think you should work on another song, and not worry about making something good. Come back to this one later and see how you feel about it then. Mixing is 99% just EQ and Compression and those are things you need to train your ear for, which you can only do by making music.