I would guess that your on/off throtle situation is due to the need for the proper accelerator attatchment.Edelbrock's #1481 Mopar throtle lever adapter should be used and will make your kickdown work properly.As for tuning-download the manual for your carb from Edelbrock's site.It can be done by reading the spark plugs (old school)but the preferred method would be an A/F meter.Standard is OK, wideband is ideal but pricey.Good luck.Your car should be capable of much better mileage. 16-18 highway is realistic.
Ron

In sixty-five I was seventeen and running up one-o-one I don't know where I'm running now, I'm just running on Jackson Browne-Running On Empty