give 1 in breakfast & 1 in dinner
For the weight - have you tried Wellness Kitten or Wellness Chicken canned food? Those two are dense in calories but still in the good range for phosphorous
Add a couple of extra treats during the day - cheese etc, try to tempt Sampson to eating a bit more per meal
And for the fur - it might just be stress
does he have a spot he can go to relax/snooze that Pumpkin doesn't go?
Did it start around the time he was diagnosed w/HyperT? If he was doing it then in reaction to the hormone levels, he may be doing it now as a repetitive motion stress reliever, unless he is showing signs of HyperT again? I know he is at a good spot now w/the T4 number.
Did you change laundry degerent/cleaning solutions/fabric softener/carpet cleaner around the time it started?