1) Rodimus, you may have heard people talking here about the mental game? Well it's time to start developing one along with everything else. Good bowlers don't pay that much attention to what the opponent is doing. They focus on what THEY are doing.
If the other guy stepping on the approach bothers you, let him bowl first then bowl while he's watching the ball or while he's waiting for it to come back whichever works out the best. Don't tell him why you are letting him go first, just smile and say "after you" and wait no matter what he says.
2) While your opponent is technically cheating in stepping over the foul line, in reality he's still throwing the ball 60 feet. The 5 inches he's shortening things really IS NOT going to give him any appreciable advantage EXCEPT for the distraction and anger that it creates in you.
The same with his silly little game while you are on the approach. He knows he's psyching you out and that's why he does it, but take comfort because it also says something about him: he doesn't have the confidence that he's good enough to beat you without resorting to cheating and head games. That should make you feel confident in your abilities if you will get your conscious mind out of the way and just let them come out.
Quiet confidence is a very intimidating to your opponent by the way. If he does something good, be polite and congratulatory, but never act concerned or worried about it, but rather with the inner confidence that it's merely a matter of time till you put the game out of reach.
3) Unless the guy actually is getting oil all over the approach, (and given he hasn't fallen yet there probably isn't much lane oil out there) stop worrying about whether he fouls and instead close your eyes and start trying to visualize yourself throwing a great shot on your next shot.
It's a much more positive use of your mental energy and you will at least be able to enjoy your bowling more if you aren't stewing over his antics. You may even find you throw the ball better when you rehearse the delivery in your mind before you throw it. Try to see yourself flowing smoothly to the line, feel the free swing of the ball. See the ball roll right over your mark and into the pocket and watch all 10 pins fly into the pit.
Another advantage of visualization is you won't be stewing over the "lucky" shots that your opponent gets away with.