Well the summer is pretty much over and I was only able to raise 5 Monarchs from caterpillar to adult. Apparently I could have raised a lot more of them if I used a different method. Basically I was only going after the caterpillars who were a week to days away from forming a chrysalis. Apparently you can collect them as early as the egg stage, I didn't do that because I believed fresh milkweed would be better for them.
A friend of mine said they released at least 40 this year by collecting swatches of milkweed leaves that had eggs on them. The interruption of their flow of sap makes the milkweed safer for young caterpillars to eat starting out. But they said still 1 in 10 caterpillars die their first day, which is still better than out in the wild where 1 in 3 die their first day. Each generation needs to be kept in it's own container, adult caterpillars will eat Monarch eggs so there's no adding to the same container.
I don't know the details on how many leaves per caterpillar are needed each day but this method sounds like it's better than what I was trying. Out in the wild birds and spiders regularly make a meal out of the caterpillars, even if it means spitting them out shortly after.