From your figures S25 and trailer combined weight of 4260lb equals a tongue weight of 425 to approx 500 lbs, you are within the specs you listed 500/5000. As long as you are not exceeding (drastically) the 'Bs' rear axle, I would say GO WITH THE TRAILER.
4 down = driveshaft disconnect , tow dolly front wheels up = drive shaft disconnect. tow dolly rear wheels up, rear over hang of bed and step bumper may put it too close to MH, turning. Some will say that in can be down, some with say that it can't be done.
Ken