Your numbers are super low, I did far more intense testing awhile back and uk isn't worth the slot. How much actual skill are you casting in?
600 enfeebling magic is -117 base before Sab or +Enfeebling potency takes effect.
(117 + 10) = 127 * 1.34 = -170.18
With Sab and gloves
(117 * 2.12) = (248 +10) * 1.34 = -345.72
On NM's
(117 * 1.37) = (160 +10) * 1.34 = -227
Using Uk boots
(112 +10) = 122 * 1.39 = -169.59
With Sab
(112 * 2.12) = (237 +10) * 1.39 = -343.33
On NM's
(112 * 1.37) = (153 +10) * 1.39 = -226.57
Uk boots lose every time though by minuscule amounts. Since those boots don't provide anything else of value, mediums's should always be used over them for Enfeebling Skill Potency spells.
Here is the formula if anyone's interested
https://www.bg-wiki.com/bg/Distract_III
610 Enfeebling skill is -120 evasion, 600 is reasonable for people to get and gives -117.