Re: I am ready to kill him ... Peeing everywhere for no reason
Since you've done the vet visit already, two thing come to mind immediately.
Litterbox. He doesn't like the litter or can't get to the box in time (too far or someone is keeping him from it). How many boxes do you have? There should be 4 for three cats. The box needs cleaning more often for some picky cats. Some cats want a box for peeing and a different one for pooping. How old are your litterboxes? Even with great cleaning, they do accumulate a slight odor over time.
Moving around. Cats love routine. Some cats travel well, but many don't. Even though you say that tolerate the moves fine, you may be missing some signals that this cat isn't adapting as well as you thought. When you left the cats with Uncle Eric, they had a quick adjustment to a new location and new person, even worse in their eyes, you weren't there. Could you have someone stay at your place when you have to leave?
Skin kids - Jason, Kevin, Allison
Canine kids - Bennett & Bailey (always in our hearts), Riley, Banker, Rogue and Boz
Feline kids - Zoey, Talley and Abra