Err also, there were still some errors in your .spine project. I fixed them and put the .spine file in the Assets/Spine directory alongside the JSON.
Most notable were the Flamethrower attachment keys. The reload attachment keys weren't clearing themselves and Idle/Run wasn't cleaning it up either. I added the keys to do that, but sometimes its just better to have 1 animation that literally is just attachment clearing keys on frame 0 and thats it for all weapons, then you load it and use Spine.Animation.Apply to forcefully clear all the weapon slots with code, rather than using the SlotsToSetupPose.