Is 68F too low for hot water heating thermostat? Final radiators not getting heat
The pressure is too low. Normally when you bleed there should be air or water getting pushed out.

Find the intake valve and open it up a bit. Then go around and bleed the radiators and open the valve again for a bit. Repeat until all radiators spit out water when you crack open the bleed valve.

Then when the circulation pump kick in again it may push some air back into the radiator requiring another bleed. After that you should only need to bleed once a year or so.