1989 Other Toyota Models lower mileage and warning lights

Engine Performance problem
1989 Other Toyota Models 4 cyl Two Wheel Drive Automatic 204K miles

I have some questions I hope you will be willing to answer. I am in a small Arizona town and usually do my own repair work. The nearest Toyota dealer is 60 miles away and I am disabled, so I need to avoid a shop if I can.
I have a 1989 Toy Van, 2WD, Auto, AC, PWR windows and locks with 104K miles. This van has a clean body and every little switch, option and item works on this beauty.
It has always run well since I bought it 5 years ago with 176K miles, well, until the 'problem' started.
I was about 35 miles from home for my daughter's track meet, driving towards home, and the 'CHG' light came on. I continued driving, hoping I could make it. The battery finally died and so did the motor. I had to call AAA. It turns out the wire from the ALT broke off of it's connection at the battery.
I repaired that and bought a new battery.
The problem is that my mileage has gone from 22 in town to 14 at best. This hurts.
I work with a Chilton repair manual and did a diagnostic by shorting the 'T' terminal. It displayed Trouble Codes # 12, 22, 43 and 71.
#12 - No "NE" signal to ECU within 2 seconds of engine being cranked.
#22 - Open or short circuit in water temp. Sensor signal.
#43 - No "STA" signal to ECU until engine reaches 800 RPM with vehicle not moving.
#71 - EGR gas below predetermined level during EGR operation.
I don't know where to start. The engine runs well (sucks gas) but is hard starting when it is below about 60' F. I have 3 different electrical sensors at the coolant fill cap. They all change OHM (resistance) value when dipped in hot water. The book doesn't say which is which and parts stores can't order parts until I can show them the part I need.
Also, 3 warning lights (brake, charge, radiator) stay on after I start the engine. When the engine is warmed up enough for the transmission to shift to Overdrive, I can get the warning lights to go out by using the O-drive switch on the shifter 5 or 6 times. The lights stay out until I re-start the engine, then I use the switch again to get them out, as long as the engine is warm.
The vacuum modulator checks out OK. I did find an electrical VSV, connected to the (I think) cold start injector, not functioning when I applied 12 volts. It is staying closed, with no air flow through it. I just found this tonight. (Sunday)
One more thing - when the outside air temp. Reaches the upper 80's, I am getting a loud ping? (Chain rattle) sound during acceleration.
The exhaust pipe is heavy with black soot and I smell gasoline when the engine is running. There are no fuel leaks.
I really like this van and need to keep it running. I want better mileage. Maybe you can help.
Thanks for your time. I really appreciate any direction you can give me.
Sincerely,
Dan Wesley
onwardup@rraz. Net