How do I properly scale damage for an armor system?

What I have tried to do is create an armor system that properly absorbs and scales down damage taken instead of just increasing the player's MaxHealth. I have been able to do this but I ran across a problem where the script stops scaling properly and the player takes more damage as their health lowers, I think I didn't go the right way about doing this and I'm stumped.

Code (This is in a script inside of the player and it also accesses a armor durability value inside of the player and I'm sorry if it's spaghetti code I haven't scripted in a while):

function absorbDamage()
    if script.Parent.Durability.Value <= 0 then return end
    local newHealth = script.Parent.Humanoid.Health

    if newHealth < oldHealth ~= true then return end

    if newHealth < oldHealth then
        if debounce == false then
            debounce = true

            local damage = script.Parent.Humanoid.MaxHealth - script.Parent.Humanoid.Health
            script.Parent.Humanoid.Health = script.Parent.Humanoid.MaxHealth

            wait(0.1)
            local scaleDamage = damage*0.60
            print(scaleDamage)
            script.Parent.Humanoid:TakeDamage(scaleDamage)

            script.Parent.Durability.Value = script.Parent.Durability.Value - 5

            wait(1.5)
            debounce = false
        end 
    end
end

script.Parent.Humanoid:GetPropertyChangedSignal("Health"):Connect(absorbDamage)