Issues with 74 Dart
1974 was the only year for the seat belt interlock which might explain your start problem. Have you checked that? See link below.
http://www.slantsix.org/forum/viewtopic.php?t=17482
This is not a cure all, but is not likely the OP's problem. When the seat belt system fails, the car simply will not crank.
The BEST way to bypass the thing is to find the reset box under the hood, and cut the two yellowish wires going to it and splice them together, here:
http://www.forabodiesonly.com/mopar/showthread.php?p=1969624169
http://www.forabodiesonly.com/mopar/showthread.php?t=14304
So far as the OP's starting problem, since he's replaced the ballast, it MIGHT be a bad connection either at the ignition switch or in the bulkhead connector.
There's a separate contact in your ignition switch which is the ONLY source of ignition power in "start." This wire comes off that contact (Mopar calls it IGN2) goes through the bulkhead connector, and to the coil + side of the ballast resistor
So far as idle, this could very well be a vacuum lean, or carburetor problems. However, TDC IS NO PLACE to set timing. I'd bump the timing up AT LEAST to 5--8* BTC