Help with creating rotational mapping

Hello all!

First of all, I am sorry for my non-fluent English. In my project, I have to match the movement of body parts between platforms. Initially, i thought about matching their localEuler rotational angle values, for example since the target Forearms yaw is limited to [-80 (lowest point), 0(highest point)], I could make a mapping for the unity model from [0(lowest), 80(highest)]. While in theory - and when testing on the editor values - this was correct, actually controlling the Unity model created some inconsistencies, like for example the rotational values: 85,-15,28 and 78,24,76 both result in the same end model placement, but one is within my mapping and the other is not. So, my second idea is to calculate how much the object has rotated compared to its initial placement and apply that to the remote model. I would appreciate any and all help!

Edit: I added an image to show what I mean:

edit2: To explain further, If in the images the Hand's starting position is near the hips, I would like to know how many degrees I would have to translate in x,y and z to achieve the image placement, without having to deal with multiple combinations of possible angles that produce the same result.