Sounds like you're saying it's more important for your flock to stay small, and for you to continue to stay under the radar than it is to produce a bunch of meat. Get a scale, start a notebook, and keep good records. Eat the birds that don't enhance for your criteria, breed the ones who do. Time your breeding so that you're not feeding too many birds over the winter - too expensive!
Search this site/google for "line breeding", which is breeding to offspring. I'm new to breeding myself, but I understand there are arguments for and against line breeding, mostly having to do with how fastidious you are in record keeping. But, with only one rooster, I think you'd have little other choice, unless you change out roosters often (craigslist generally has plenty of listings for unwanted roosters). That means you'll need to set up a breeding pen or trap nests after your first generation (so you can keep track of the parentage of each egg). I've got 4 roosters and all my birds range within a pretty good size area of pasture/woods. I'll be rotating paddocks to control parentage, rather than putting the birds in pens. It's a little bit loose (I'll know the father and which group of hens an egg is from, but not which exact hen), but I think it'll work for us.
You didn't mention what kinds of chickens you already have. Keep in mind that hatcheries make money by having hens that lay lots of eggs for production - so even their "dual purpose" breeds are heavy on the egg laying and light on the meat making. I've collected a variety of heritage breeds that I've been curious about and started breeding them last year to build my own homestead line of hearty chickens suited to my environment, interests, and style of husbandry. The offspring of hatchery birds are vastly superior to the parents, amazing how much more glorious the birds are in just one generation! Can't wait to see how they progress through several generations.
To support productive brooding, have a very inviting nest, write on the eggs you give the hen to hatch, and keep good notes. I find that hen raised chicks are better foragers and hardly need dishes to eat from. My alpha Marans hen was a great mother last year, as was a Dark Cornish. My alpha rooster, an Australorp, fathered some big kids with a Barred Rock and the Marans. We've got a La Fleche trio - they are smaller birds, but super tasty. Also, the La Fleche rooster is not too loud (he's my beta roo). So far, Buff Orpington roosters, though they grow fast enough, have been too loud and goofy for our flock - they're devilish, even the second generation. We ate our Silver Dorking cockerel (who was stunningly beautiful), but kept the three hens; they were fast growers and I'm looking forward to some big birds when I cross her with the Australorp. Our Javas looked big, but weighed no more than the heritage Cornish (White Laced Red), since the Cornish are so dense. I'm going to cross some heritage Cornish with the bigger dual purpose boys this year to see if I can get the density of the Cornish into a larger body. Heritage Cornish aren't supposed to lay as many eggs as, say, a Barred Rock or New Hampshire, but mine lay PLENTY!
It's really fun to breed, raise and eat our own birds. Killing never gets easier, but it feels really right.
