Just a few thoughts....
Hang in there, hopefully we can come up with something that will help.
A lot of the puppy pee pads have an attractant in them to encourage puppies to use them. If possible get the unscented ones, just in case he is viewing the attractant as an invitation to spray.I have the pee pads taped on on the wall. I have also period pads (an absolute eyesore) on table legs too, because he will pee on those. I recently got the XL puppy pads few days ago (used to use smaller ones and TONS of paper towels) and for some reason, he seems to be really scared of those? I'm not sure if it's worsening his anxiety, I'll have to check back on this.
Could you move it right into his pee corner with the pee pads still taped up to the wall behind the litter box?I moved his litter box closer (a foot away or so?) from his pee corner a year or two ago, that didn't help.
Zylkene comes as a capsule that you break open and mix with their food. The cat I have that needs it is way too feral for me to ever pick up and pill her. Zylkene is made from a milk derivative, so the way that works best for her is to mix a dose with some of that cat treat milk you can buy and give it her that way. They don't seem to notice it mixed in with their wet food either though.I will be talking to my vet about Zylkene as well
Try crushing up some of the dry food they love and sprinkling on top of their canned food. Sometimes the taste and smell is enough to encourage them to eat more of the canned. Don't mix canned and dry together though, as the dry food gets wet and this can allow bacteria to breed.Do you have recommendations on trying to decreasing the dry food for two cats?
Hang in there, hopefully we can come up with something that will help.