That's an insane take. If someone presents you that opinion it should immediately discredit their opinion.

I realized I didn't answer your question. Don't exceed 60psi for well tanks. I would stay closer to 50 myself. They aren't designed generally to exceed 60.

Generally you should be able to run a jet pump at a higher pressure. If it wasn't capable it should list that which yours doesn't seem to. Hard to give a definite answer as all pumps as a bit unique despite being very similar.

Reading your question again it's clear that you're not worried about maximising life. If that's the case I would turn the pressure switch up and test it at a higher pressure, deliberately cycling it to see how to responds. If the pump on time is reasonable compared to the factory 20/40 then it should work for now even if it's shortening the overall life of your pump.

Just because it's a higher horse power doesn't mean the pump is designed to achieve the same head pressure. You can have a 50hp pump that's designed for low grade pressures. If your pump cannot generate enough pressure to counter act the cost of lifting the water to the height of the second floor that's why your flow will suffer.

If I remember correctly it's approximately 1psi lost per meter increase in elevation from pump.