I'm not sure if this is the issue, but has the acceleration value always been 200 because that might be the problem considering the fact that it's acting as the weight for the linear interpolation. I would try lowering it to like 5. Otherwise I don't see anything that would cause that. I guess that's the point of forums, since you can get multiple perspectives at once.
While I have no experience with shaders, in Godot any variant can be converted to bytes by using var_to_bytes and bytes can be converted back again to variant using bytes_to_var
var v3array : PackedVector3Array = [Vector3.ZERO,Vector3.ONE,Vector3.LEFT]
# To convert it into bytes
var v3array_bytes : PackedByteArray = var_to_bytes(v3array)
# To convert it back again from bytes to PackedVector3Array
var convert : PackedVector3Array = bytes_to_var(v3array_bytes)
I'm not too well-versed in the Godot engine thus far, but my best guess would be to check that the texture's filter is set to "Nearest" as opposed to anything that blurs the pixels like "Inherit" or "Linear"
I'm not sure whether or not you've figured it out by now, but for mobile devices you need to use buttons as your controls, as it's the only feasible way to interact with the Godot engine at the moment (besides tapping the screen). As for tutorials I would look to the Godot documentation on UI elements, or watch a tutorial on buttons.
Man, I need to start solving my own problems, because at the expense of around 10 hours of my time and a little bit of sanity, I've finally fixed it! For any of you trying to make a movement FPS in Godot for whatever reason, you can use this as a base. It's klunky, but it works:
I have officially found the issue, and it seems to be that as soon as I enable autoload on literally anything, that's when the node system stops working, so for those of you who are seeing the same issue, I would avoid autoload because it seems to be VERY buggy.