2pipe/1pipe system

Sean_7

I have a steam heating system that never worked correct since it was converted from oil to gas and from 2 boilers to 1 boiler with 2 zone valves. Heres how it looks:
#1 Zone feeds an Attic ducted fan coil unit (2 pipe with an F&T returning to a condensate tank).
#2 Zone feeds 1 pipe radiators. Several supply lines run to different areas of the house teeing off the line to the radiators and at the end of the lines is a F&T with a vent returning back to the boiler.
What can I do?