40mph up a 7% grade running a gas V8 @ 3k RPM while pulling 4k+ of TT. What exactly is the OP's question, because "is this ok" or "does this seem right" depends what your asking.
Is this ok at full throttle? Heck no.
Is this ok to do on purpose? Sure
But why would you do this on purpose? Do you feel better about going 40mph up the 7% grade when you could be going 55mph without breaking a sweat? Grrrreat. Just don't get in my way, cause I could pass you pulling the same weight towing with a Honda Pilot. (That's a fact)
If your doing just because you think its easier on your motor...well...that's a BIG misconception and you aren't using your motor as designed. Gas motors are designed to REV to MAKE POWER! SO REV IT!!!