Your oil pressure sounds good to me, drive a steady 60mph and the pressure should also be roughly around 60 (gd little test).
The rumble should be detectable if you aim for a mild bump or divot in the road, aim one wheel at it and listen before the back hits it. Although the compression arms are usually not as constant as in that video (unless your one a really rough rubbly road?) so that makes me wonder what it might be (if anything else).
The noise in 1st and 2nd or probably 1st to 2nd, will be the flywheel, they clatter quite a bit and you can also hear it when depressing the clutch the noise should stop. Its all normal, just make sure its not groaning or whining.
Some more investigation into your rumble though, try the bump thing slowly to try and find the front or back wheels as the issue.