You're certainly doing everything right. Is there anyway you can call your vet (or a local vet hospital) to see if they could care for the kitty while you're at work. Or, if you're not going to keep the kitten, see if they'd want to care for it and find it a home. Kittens get adopted very quickly.

Another suggestion is to search for the other kittens. Watch the mama and her comings and goings. She won't stray far from them, trust me. It's way too soon to try and trap her, as her kittens need her more. But when they get older, you might want to trap her and the kittens. The longer they stay with the mama, the more difficult it is to socialize them, as they become feral (wild).

Keep up the great job!