Can I save my info and sign back in on Thursday to finishthis? I'm at the very end and I need an id number I don't have right now

Yes, TurboTax Online automatically saves your work as you progress through the tax interview. When you sign out your progress will be saved and you can sign back in and file your return at a later time. To sign out, simply click Sign Out at the bottom left of your screen.

Yes, you can leave and come back later to finish.  Click My Account and Save and Sign Out.  This will ensure that your progress has been saved (though Turbotax automatically saves your progress as you work).  And, this will securely log you out of TurboTax.  You can close out of your browser afterwards and log back in tomorrow (or whenever you wish to proceed with the final steps).