"ACA" I don't know if people show those dogs
Not really- this registry is used mostly by pet stores and puppymillers- so it doesn't bode well for his conformation prospects.
Still, if you're serious about breeding him, your first step in the right direction would be to get him registered with AKC or another like registry (as Rhinecat already pointed out), and get him in the conformation ring (where he can be evaluated by Pug judges), or at least into some performance events).
In all honesty, I think you'd have a LOT more fun getting your CURRENT dog involved in an activity you can both enjoy, rather than breeding him.
Agility would be fantastic. It will strengthen your bond, and is LOADS of fun for BOTH dog and handler. Should you decide to join an agility club, I can guarantee you'll make great friends, and have a wonderful new skill set you can be proud of. The physical activity does wonders for stress relief (in both dogs and humans), and all in all, you'll have a happier, more relaxed buddy.
While a performance event is likely to REDUCE the stress in your home, keeping an intact male is likely to INCREASE it. Intact males are generally less biddable. They're more prone to becoming "escape artists," so be sure your fencing is MORE than secure. They're attention is a lot more flighty, because let's face it...you'll never be more interesting to them than a bitch in heat. Be prepared to be virtually ignored when your male encounters a girl in season. The inconsolable whining, the drooling, the frenzied panting...when an intact male is within a couple of MILES of a bitch in heat, I've been there. And it ain't pretty. Annoying does not even BEGIN to cover it- and this behavior will last as long as the girl is in her heat cycle.
As far as marking- there's a really good chance that should you allow him to remain intact, he'll do it. There are special "doggie diapers" that some people use, but these are a hassle, and most breeders opt just to keep dogs and bitches separated.
Extra money is always nice
If this is true...I would shy away from breeding, LOL. If you're doing it RIGHT you will almost always LOSE money.
You'll need to get his hips tested (done at 2 years) by OFA. CERF testing is a must as well. If you don't know what the acronyms stand for yet- it'll be your duty to research that, BEFORE you breed your dog. It's part of being responsible for the lives you're bringing into the world.
And yes, while lots of people "love and want Pugs," lots of people DON'T want Pugs with hip dysplasia, seizures, cherry eye, luxating patellas, or progressive retinal atrophy. I see these guys in my local humane society on a WEEKLY basis- you can bet they were all the results of breedings done by people who didn't know about genetic health-testing, showing their dogs, or didn't care.
I'm not sure what the main genetic disorders in Pugs are, but you'll need to look them up and have him tested.
A canine brucellosis test is also a must. Sexually transmitted diseases DO occur in dogs, and brucellosis can cause a dog or bitch to become sterile, among other things.
Your puppy is very young- still a baby, and it sounds like you've got a lot on your plate. Do you really want to add all of the above? (Or worse- should you choose to forgo testing).
I think it would be a fantastic idea to get involved in some kind of an activity with your CURRENT dog. You sound like you want what's best for him, and you're striving to be a good owner. Show your pup you care about HIM, and get involved in something fun, like agility! ( I promise it's WAY less stressful than breeding!)