1994 Ford Escort Car shuts off unexpectidly

Electrical problem
1994 Ford Escort 4 cyl Front Wheel Drive Manual 200k miles

the symptoms are,

the car shuts off, like a switch for two seperate conditions.

1) if I use the rear defroster, it takes about a minute, the car shuts off. Every time. The car will re-start after about4 minutes.

2) I can drive it for about 20 minutes, less in hot weather, and more in cold weather, and then, the car shuts off. Usually it will re-start after about 4 minutes, but if I keep driving, the interval to shut off gets shorter, so next trip, maby 5 minitues, and the cooldown time between starts gets longer, maby 7-10 minutes.

when the car shuts off, I can hear a click, like a relay and the dash lights go out. When I can start again, the dash lights up.

The ecu tests good. (Im thinking im going to change it anyway, but it tests good)

The car runs very smooth, starts first try even in cold weather.

it has started running rougher. Like a clogged fuel filter maby.

when I got it 9 months ago, I was getting 40 mpg, now I get less, like 25 maby

Parts I have changed/ checked.
Fuel filter, changed
Fuel pump, pulled and inspected, it looks good, no debris etc.
I changed the plugs and wires.
the plugs look, ok for a car with 200k miles, cylander 3 is leaking some, scorch marks on the side of the plug.

Any advice is appreciated.