Y axis wont rotate past 90 degrees and instead flips around, please for the love of god help im going insane

So im working on a view model for my game right now but ive noticed that whenever getting the rotation it flips around at 90° causing both 100° and 80° to both come up as 80°

The issue is i very much need it to NOT do that. but as of right now i have absolutely no clue how to get the rotation without it flipping around at 90°

Im not too sure how well i explained the issue cause its a bit hard to put into words, so i made a super duper helpful not at all quickly made chart to hopefully explain it a bit better

Please help i am going to go insane

Edit:
I didnt actually explain what the main issue was too well so heres a second shot at it
I need to get the difference between 2 y axis rotations.
the issue is the difference is incorrect when it reaches around 90° due to it just going back down instead of going to 180 (0>90>back to 0 instead of 0>90>180) causing the difference to not be accurate.
The properties window displays the correct rotation. but when i actually call it in a script THATS when it stops at 90

local Rot = character.HumanoidRootPart.Rotation.Y-character.Torso.Rotation.Y
local CF1:CFrame = (camCF*CFrame.new(1,-1.35,-.75)):ToObjectSpace(torso.CFrame):Inverse()*CFrame.Angles(0,math.rad(Rot),0)*CFrame.Angles(0,math.rad(90),0)
rightShoulder.C0 = rightShoulder.C0:lerp(CF1,updateSpeed)

Heres all the code that calculates the cframes and whatnot. math aint perfect, and it may or maynot actually work correctly rn cause i hastily slapped it back together after testing hopeful fixes for like, an hour with no luck, but its mostly correct
I am 100% certain that i can get it working correctly after i get past this roadblock.

you may have already tried this, but does it work if you put it at -90 or 450?
(Last part of second line)

the last part of the second line is to fix the position of the arm so it isnt backwards

Heres a video to physically show the issue, i can easily fix it being inverted in one direction but normal in the other. the issue is the fact that its a transition between inverted and normal thats making this so difficult

Incase anyone has the same issue at some point, i found the issue
I was calling Rotation instead of Orientation. thats all. cause APARENTLY their different