I see you haven't installed Padmee's BG3 Tools for Blender, so I have no idea whether everything will be imported and exported correctly so that it is displayed correctly in BG3.
From a glance it looks like that's just a collection of scripts for basic things; i don't have any need for that. As for matching the rotation; I've tried many combinations but I can't align both the weapon AND vfx correctly at the same time. If you can with blender .GR2 export then I can try again.
I could explain the full method for weapons and armors but i suck with explanations so you should go to the wiki or to the discord to get more info, also theres a cmty discord where you can find a basic guide to import a weapon so you can get the correct armature for your weapon,
https://discord.gg/bg3modsOk, so I tried this, and after some initial issues I got the LSlib .gr2 export working with copy skeleton. and it imports into the editor, however it crashes upon save (converting the mesh). I'm going to try again with a different model and skeleton.