Is growing cilantro outside an option? You will get best results from that.

Cilantro, like parsley and a few other common herbs with taproots, resent being transplanted. Any fiddling around with the roots causes them to bolt. Direct sowing into the ground is best but if you can't do that, direct sow in the pot they will be growing in - no transplanting.

Plants getting the right amounts of light, air circulation, and moisture really don't flop over. I'm not sure if you mean the plants are weak or if you mean the rather fountain/spray like shape the cilantro leaves take when they are producing leaves well. I'm assuming weak seedlings. Pictures do tell us more of the story so please post one.

Harvesting the leaves is at any time you want. But if you have to wait until the baby plants get some size on them. Looping all the leaves off a baby plant is a recipe for disaster and no real harvest.

FataMorgana

PetiteLoup ; if you would post your zone that would be a great help when others reply to your request. As for knowing when to harvest your Cilantro that you will know as it will look a lot like those you see at your grocery store. I am able to harvest with them coming back again to harvest later. I always let one plant go to seed near the end of our cool season for the seeds to plant the following fall season. They do love cool weather, the warm weather makes them bolt and produce their seeds. It they start to produce fine fern-like leaves it is bolting.