Post the answers to remaining questions when you have time.
How many miles on the D15B7?
Are you the original owner? Or did you just purchase vehicle?
1) Short the two pins in the service connector located above the ECU, and then turn key to ON(II). Watch the check engine light (CEL) in the cluster blink the trouble codes.
2) Remove a plug wire from a spark plug. Insert a new spark plug into the plug wire and then ground threads of the spark plug on valve cover (metal). Have buddy crank engine while you watch for spark at end of plug.
Why did you buy the car if you knew the engine was badly misfiring? How much did you pay?