how about this they survive of of pests, now bare in mind that if a dog could kill about 50 of these things if they were unarmed i don't think that they could really hunt anything larger than a cat. now if the could hunt vermin fish eat moss and plants and grow them they probably could survive
A. Even dwarves can eat vermin (in emergencies). It's just not respected in worldgen yet,
B. Actually, dogs can't kill "about 50 of those things," because metal dagger+clothes>no armor/weapons. One-on-one, the dog would have a chance, but 50-to-one means the dog's kibble.
Assume that they have about the same mass-to-calories-consumed ration as a human. That means that they eat a bit less than 1/3 of what a human does, because IIRC kobolds are size 20,000 compared to humans' 70,000. So, about one human-sized meal per day...say, one steak with some wild rat on the side or the equivalent, daily. Assuming that that one unit of meat = 1 real-world steak, that means that 23-27 kobolds can be fed for about a day on one cow slaughtered, and still leave the fat and bones. If they subsist entirely on parasitism, that means that kobolds are unlikely to be numerous or form large settlements. But if each unit of meat feeds a human for a week or two (as dwarves are sated by one unit of food about every that often), then a single unit of meat (~5% of a cow) could satisfy an entire kobold village's hunger for a day or so (depending on the size of the village; assuming around 50ish), which allows a fair population of kobolds to steal meat from the tables of humans.
I think that they should be more like Vikings were, but exaggerated into their "raider" role and mixed with...something stealthy and land-based other than ninjas. They make their own food (raising cavies or cats or chickens or something for slaughter), letting them forage in the summer and gathering rats for winter, and raiding for stuff they can't make but want. Which, having little more tech than smart apes in a society that includes steel, is a lot. They support these thieves on a combination of surplus livestock and, yes, stolen food.