The coach manufacturer's "recommended psi" is sufficient for the coach at its maximum weight. Has to be, since they have no idea how much cargo & passengers you will be carrying. That means the tires may have a relatively high psi if the coach is lightly loaded. If you got scaled weight for each axle or each "corner", you could optimize for the actual load instead of max and sometimes that makes a noticeable difference. It would also show whether the balance of the load (front vs rear) is reasonable or not. You have a large coach for that size chassis, so it's likely you need that tire psi, but best to check it out at the scale. Fleetwood should probably have used the 24,000 lb Ford chassis instead of the 22,000 lb version, but they are always trying to keep the price down and often lowball on things like that.
Generally, though, what you are experiencing is more-or-less normal for that type of chassis. The sides of the RV act like a huge sail and any wind (natural or passing vehicles) has a dramatic effect. Two things happen: (1) the entire chassis gets pushed sideways and (2) the spring suspension leans and shifts, applying sideways pressure to the steering. In effect, this sideways pressure throws the front end alignment off.
Adding a rear track bar usually helps the suspension shifting problem. So will a stiffer anti-roll (aka anti-sway) bar than what Ford supplies from the factory. Supersteer makes a rear track bar (aka panhard rod) for the F53 chassis.
Not much can be done about the sail effect, though there are remote control steering adjustments that can bias the steering to counteract a sidewind. Those work ok if the wind is a constant velocity, but are of little use when its gusty or for passing vehicle because the side-pressure changes moment to moment. Some people add a device called a Safe-T-Plus to help dampen the steering action. I'm not a fan, but others claim it helps quite a bit. It slows the steering response somewhat, so that may make it more comfortable (or more predictable?) for some folks.
Some years ago I wrote an article on Motorhome Handling and it's in the RVForum Library. It's a little bit dated now, but might help you understand what is happening and the products available to assist.
Motorhome Handling