Well, you can start clipping clones whenever you want, but it sounds like you've kind of jumped head first into the deep end, perhaps trying to start a sog type operation off the bat. You might want to just focus on the one plant you have right now.
And really, you're probably doing too much worrying about your plants. Plants need some time where you're not doing anything to them in order to respond to what you've done. You aren't necessarily going to see results in an hour.
Don't pull anymore seedlings until they are totally pulse-less.
You can take clippings from a plant in veg or flower. That means it's had time to make it through its seedling stage and into veg. A clipping taken in flower will need 24/0 light so that it comes out of flower. A clone is literally in the same stage of life as its mother. That means a clipping taken at 4 wks veg will be at 4 wks veg once it gets over its shock and takes root. This is one of the most stressful things a plant can do.
I don't think I'd worry too too much about clones and clippings at this point. I know the curve seems slow, and it is, this is not an overnight process. But you'll get it.
Try and make sure you learn as much as you can about the maturing plants you have now. And try not to lose any more seedlings. This might mean that you have to make sure your not treating your babies like Elmyra from Animaniacs might.