Totally agree, leave him in there, let him get those others going..You can remove it any time technically, if you have the brooder ready. Most wait for them to dry and fluff up. BUT, you don't want to open the lid any more than is necessary. So I'd leave it until you have at least another one hatched. You don't want to dry out the pips by keeping opening the lid. Especially with your humidity running on the low side.