The ignition switch on my 2000 Ford Focus would not turn. I had to have it replaced. One year later it is periodically having the same problem, but I keep a very small hammer in the car, and all it takes is a couple of taps on the key for me to be able to turn the key. BUT... now it seems that the clutch interlock is not working intermittently. Sometimes, it doesn't matter how hard I push on the clutch, I can't crank the switch that final turn - and then sometimes it works fine.
Does anybody know the process for testing and fixing the clutch interlock? Thanks

I don't believe it's a clutch interlock problem, but an ignition switch, key, or lock issue. Remove the column covers and check things out.