98 subaru legacy wagon 1 dead cly but has good comprestion???? 100lbs

Which engine do you have? Unless it's turbo charged or Diesel engine your compression ratio is either 10.5:1 or 10.0:1. Your psi should be running 157.5 to 210 psi (10.5:1) or 150 to 200 psi (10:1). If you at 100 psi that's way to low. What are the psi numbers on the other cylinders? Add a little oil in that cylinder and see if psi rises. If it does then its a ring issue. If it does not its probably a valve issue.

Also if it's the 2.5L that's an interference engine. Meaning if timing belt breaks, jumps time or is not installed properly the pistons can come in contact with the valves causing bent valves.