was air pressure ever higher than 1 atm in ancient time?

Yes, that is why there are fossilized foot prints of ancient creatures. The increased air pressure pushed them into the soil more, causing the creation of foot prints.

Air pressure is all around doesn't "press down" ever scuba dived?

I don't know the answer but I throw this into the mix. It has been suggested that the Pterodactyl could not have flown today as the buoyancy provided by he air would not support it. It has been suggested (but you may already know this) that the CO2 content (and hence air pressure) was much higher then if these creatures where to be airborne.

Excellent question. The answer is...maybe.

There are three prevailing models [See source.]; one shows a HUGE atm pressure (perhaps 90 atm) in the very beginning, another shows one in the 5 atm region, and the third shows just the 1 atm as Earth began.

Interestingly, all three models converge on the planet 65 million years ago when the dinosaurs were wiped out by that big meteor off the Yucatan Peninsula. At that point in time, the pressure is guesstimated at about 5 atm for all three models. Which means, for the 1 atm model there was a major spike in pressure [from the meteor impact?].

yes