Let me get this straight:

You're asking if you; who by both your own admittance, and the level of questions you are asking, seem to have very little towing experience, should tow a trailer several thousand pounds heavier than the tow rating of the vehicle you wish to tow with, at highway speeds, for a long distance, and over significant grades?

Does that about sum it up?

If so, I feel confident in answering "No". No you should not. Aside from the damage you may well do to your own tow vehicle, think about the safety of the other users of the roads. It's not about can your tow vehicle drag something that size up and over Pacheco Pass, or if it stops nicely from 60mph on a straight and level road, it's more about how well both you and your combined rig (tow vehicle and trailer) can handle a sudden double lane change in the middle of a downhill curve at speed when the unexpected happens.

Please, think of the others on the road, and the hazards your decisions may present them with.

MV