spaceman

hi, just a few questions about the stock is300 and rpm rate:

1. will running the rpm between 3 - 4 rpm on the highway cause unnecessary engine wear? i drive about 70 - 90 miles a day on the highway. i read in the owners manual that the car should be run between 2 - 4 rpm. but, i have heard that a car, in general, should be run at 2 - 3k rpm as a good rule of thumb. i just can't see driving 70 on the highway

2. i hit 3k rpm at 70 mph on the highway ( & running a little above 3k rpm at 75 - 80 mph). is this normal?

thanks in advance for any help given (forgive me - i don't know anything about cars).