Pete, our kitties were younger when they got neutered, so they weren't ever marking territory, so I have no way to compare how much they were peeing prior and after.
In answer to your other question, we let them free feed on dry C/D. We have four males and three females - three of the males have had problems. The other male we brought in one year and 4 months ago, and he was about two when we brought him in, though we had him neutered at about 1 1/2 years old. We were never aware of him marking territory prior to being neutered. He was scared when he first came inside, and even though we provided him his own litter box, he only would go once a day - one huge, giant pee. Hopefully because he's on the C/D diet with the rest of the boys now, he'll never develop a problem.
As to the other three.... I don't know if the problems would have developed if they were eating garbage and hunting mice - or if we'd had them on a raw diet. I suspect it is the diets we feed them that create the problems. Years ago there was a bigger problem with struvite crystal formation in male cats. Pet food manufacturers started adding more ash or magnesium or something (I think it's the magensium) - and now vets are seeing a much higher incidence of calcium oxalate crystals. The big problem would be what we're feeding outside strays/ferals - and not seeing the problem in peeing - because the urethra of the male is constructed in such a way that they can get blocked with a plug of crystals pretty easily - and then it's 24 - 48 hours (depending upon how much they drink) before the toxic urine backs up through their kidneys and kills them.
We simply knew there was a problem because they'd either start trying to pee outside the box, or were in the box with increased frequency. They all blocked at different times, but all three had to be catheterized at some point, one of them three times. This generally happened with each one over a several week/ month long period - all of them when they were somewhere around 2, I think - and that's when we just switched to the Hill's Science Diet C/D. We'd already switched to some "urinary tract health" food - but that just didn't do the trick. Thankfully, given enough time on the c/d diet, they seem to be doing just fine now. Stress, however, does play a role in bladder problems - and let's face it, being transitioned from feral to house kitty is kind of stressful (at least at first!).
Anyway.... to finish the question, we feed them only one wet meal a day. That is the canned C/D. We add the pumpkin and the warm water to the wet meal we feed them around dinner time. The pumpkin we add only for the fiber (and in the amount we add it, they all seem to like it. Two of them will eat it plain - but they don't like any other squash. Go figure). We also add the water for hydration. You've increased his fiber through using Z/D (or whichever one it is).
And yes, they should probably be given at least another meal of wet food a day because they eat so little at the one meal they do get. ...But these guys really never liked wet food much, and would never eat much unless it was just "junk" wet food.
It had to be treated more like a "treat" - which is just another argument for giving it to them more frequently - but our schedule was such that we just weren't able to give them more than the one wet meal at any consistent time, so that's just how it's worked out for them.
I thought our cats went nuts for the feathers - but they went even crazier for the mouse attachment! I mean - back flips and leaps like I've never seen before!
I am so sorry. 
I wonder what happened to poor dear Tabby.
