you should be odb2b, as for the temp gauge i believe its only the 01 and up models affected as the temp gauge shares the same sensor as the ecu instead of the sensor under the distributor. sorry i dont know about the fuel pump. but i dont see why it wouldnt be working.
one thing i learned as being a trucker is everything is your(truckers) fault. if you were parked near a back up zone it is the truckers job/responsibility to get out and look before backing up. hence why he was paying for your bumper through ebay. he would get in trouble with the company if they...
can you post a vid of the engine bay, with the car running? and i dont know if they mentioned it in the thread. but have you tightened the throttle cable to see if it might be too loose.
i dont think you can mod a obd2 auto ecu to manual. with obd1 you can just de-solder 1 connection. i think the manual ecu would be best in the long run if it turns out to work just fine with the engine.
he needs to keep it obd2 though which is a hard thing to do lol. there is a odb2 ecu that you can use that doesnt have an immobilizer from a 96 prelude. or you can try using a h22a4 ecu and have the immobilizer removed.