It looks like the brand of tire may be one that Workman has made for themselves. I haven't seen a modern bike tire that doesn't specify a maximum pressure or pressure range embossed into the tire sidewall. It might be the same color as the sidewall so a bit hard to see unless you look closely, If you ride the bike with too low a tire pressure you can get pinch flats going over a bump. At the upper end of the pressure range it can give a harsh ride but that's a trade off between comfort and efficiency. It's harder to pedal a bike with really soft tires. There is a safety factor built in so you should be able to ride the bike at the maximum given on the sidewall without blowing a tire.
There are lots of tutorials like this one
on how to adjust the tension on the bearings. Really good wheels will oscillate back and forth with the valve coming to a stop at the bottom but who knows what the quality Workman uses. It is still worth your while to check the adjustment,
I wondered about the bike weight. 75 pounds is a lot to pedal under any circumstances but Workman built the bike to withstand heavy riders. You might check out the Clydesdales and Athenas subforum here for hints on what other heavier riders experienced
https://www.bikeforums.net/clydesdal...-200-lb-91-kg/