Eventually, the rust "should" clear out (unless it is iron bacteria..., which, though unsightly, is not a health hazard..., it may build up the iron in your blood?). If you are going to stay in the house for some time, I would invest in a good fiberglass bladder tank and scrap that galvanized item. As for iron removal, there are specific water treatment filter units (far different from the little sediment filter which was installed on your system). Do a google search on water treatment and you'll get a full education on the issue.
If you look on the inside of the plastic cover on the pressure switch, you will see what the "cut-on/cut-off" pressures are. Most switches are 20 or 30 "cut-on" and 40 or 50 "cut off". If yours is a 20-40 switch unit, 39 pounds of pressure is "right on" (the pressure switches can be adjusted a few pounds either side of the factory setting and, given the fact that the gauges are not precise... 39 pounds of pressure may actually be 37 to 42 pounds in actuality.
Just recognize that, unlike "city water", your water pressure is never going to be as much as you wish it was..., but you get used to it!
BTW, 3 minutes to reach "cut-off" from "cut-on" is fairly normal for a non-bladder tank of your apparent size (80 gallons?)! Also, for future reference, the bladder tanks, due to their construction, are equal to much larger non-bladder tank sizes. Also, the larger your tank, the less often your pump will have to cycle and the longer it will last (it is the "on-offs" which wear..., just like your heart beats..., you only have so many available for the life of the unit (whether a water pump or a heart)! So, if you get a new bladder tank, don't "save" on the size..., tanks are a LOT less expensive to replace than submerible pumps!!!
You have posted great answers on both threads.