I believe your pulse rate is well up into the acceptable range, even with the slight variations, so I wouldn't worry about it. If the signal is too weak or intermittent, your machine might have problems running well, but it would never damage the machine at all.
Have you run the "drivertest.exe" file in the root directory of Mach, yet? I think that may be where you got the numbers you posted. When you do, it will give you a graphic of the performance of your parallel port. If that graphic is clean, you're golden! (The best way to show that to someone else is to take a screen shot, turn that into a jpg file and post the jpg.)