So I can’t find my ID and I don’t know if the DMV allows walk ins.. would I be able to use an expired passport from when I was a child to get through screening???

Not at all you need to have an valid ID, however you can call check if anyone return it.

No the TSA will not allow you through security checkpoints without a current valid id. Has to be issued by a state or federal agency. No work id is acceptable

No you can't use anything that is expired

I don't think so. Like was mentioned, you'll need to call.

Probably not but you should call to find out. Good luck