How do I fix these wonky and uneven curves??

How is this built, can we see the outline? It looks like you have 2 paths for a stroke inner and outer, then filled as a compound shape. Is best to build with strokes rather than fills on a compound shape.

I wodl build the inner blue B with storokes, then when perfect you can outline the strokes and joining in pathfinder for a perfect shape. Then in appearance you can add strokes to that using offset path, and choose either square or rounded joins.

Mike_Gondek_0-1765207546465.png

It's fairly difficult and time consuming to create outline effects by hand around existing shapes and end up with results that are accurate.

You'll have to start with the dark blue "B" shape, using it as a source to create duplicate paths around it. Like Monika said, the Offset Path effect is one option. Using line strokes is another option. You'll need to create duplicates of the "B" shape when applying and expanding these effects.

Depending on the shapes being offset, sometimes it's necessary to go back and make adjustments to new paths. There are rare occasions where math creates results that don't look right.