Take a look at the pressure ratings on the sidewalls of your tires. Mine are the 20" and have a max of 44 psi. I am running them at 40. I would suggest running them just a couple lbs below what the max is and see what happens. Also it depends on the road surface, freshly paved parking lots of asphalt or freshly sealed ones will squeal easier than old concrete roads. Also smooth concrete will allow tire squealing such as in a parking garage.
As far as turning your steering to the lock (end of travel) you are hearing a valve that is diverting the pressure so you don't blow a hose. I have always been taught to turn to the lock then back off just a hair so it isn't holding that pressure for a long time. You really won't change your turning radius and will allow the pump to live longer.
2009 Dodge Ram 1500 QC sunburst Orange
2010 Dodge Nitro Detonator Stone White (wife's ride)
3 Siberian Huskies 2, 3 and 4 years old and a good ole dogsled. Much more fun than any vehicle!