you should be able to fill the system at about 3 gallons per minute with a perfectly clean
It sounds like I would have the radiator checked by a local shop if it is only "trickling" in.
No thermostat would cause the coolant to flow too quickly, make sure you have a thermostat. Is the pump actually pumping?
Stop and go traffic = no air flow if your fan isnt moving air.
Have you tried at least a piece of cardboard in front of the radiator to check airflow? A good system will hold a half empty box of cheerios in place (or a 3/8" thick magazine). A bad system wont hold up a piece of cardboard. If it cant hold a piece of paper, there is no appreciable air flow.
