[Mike_The_Grad]

Try not to let either reservoir run completely dry. If it does, you will have to remove the master cylinder and bench bleed it.
By the looks of one of your original pictures, it's probably a good time to replace that vacuum line and check valve,along with the rubber grommet that goes to the brake booster. Probably cost you less than $10 for a new valve, grommet and a length of vacuum line.