emission control causing rough idle?

Flickering lights are an indication the charging system needs attention; we'll get to that, what's your line voltage at hot/slow idle with the car in Drive?

Pull EGR stem to kill engine means EGR valve is probably sealing properly. It could be causing a rough idle if there is a small leak through it, but I don't think you'll see improved idle quality by blocking it off, but it's easy to try, so go ahead and try it if you like. Buy a new EGR valve gasket, remove the valve, clean the mounting surfaces, install the new gasket, and install the valve upside-down from its original position; this will block off the EGR just as surely as any blockoff plate you might buy or make.

There will be no "air/fuel mixture imbalance" (?!) of any type as a result of disabling the EGR, and you will not need to do any rejetting. However, you may encounter spark knock on acceleration, because the distributor advance curves were set up to take EGR into account.

Have you checked for timing chain slop? Remove the distributor cap and turn the engine by hand (w/fan and belt) until the rotor starts to turn. Keep one eye on the crank pulley and the other on the rotor as you then turn the engine the other direction and see how far you can turn it before the rotor starts turning.