What did the tips of the old spark plugs look like?
Can you feel a miss when driving or is it only at idle?
Common issue on the 4.0l is a dirty MAF sensor, easy to clean though.
Good read here on it: Ford Ranger Mass Air Flow Cleaning, Removal and Installation
For ABS code 12 check the 3 wires on the side of the master cylinder, you probably have a loose or broken wire.
Pull on each wire, usually one will pop out, the bad one, lol, you can usually fix it by pushing it back in.
You have two O2 sensors, these are rated for 100,000 miles so........wouldn't hurt to get new ones.
They won't cause the miss but can cause rich running, so lower MPG.
Check the clutch reservoir on firewall, make sure it is full, hard to get into 1st with engine running and stopped, means slave isn't disengaging clutch disc enough, so you could have some air in the system and may need to bleed it.