I ran up against same issue when trying to replace rear bedroom window frame. It turned out that there is a stiff rubber like bezel trim flange all around the inside frame. The bezel locks into a groove extruded on the window frame this needed to be pried - popped off first. I think then the window is free to fall outward so you need a helper outside.
I would expect same hold true for all the 2003 Dolphin windows. Hmmm except my rear window which has the screws exposed on the inside.
2003 34' Dolphin 5342, W22, UP, UPGBrake, F and R Track Bars, Rear IPD sway bar, Koni FSDs, Safe-T-Plus, Scan Gauge II.. 2004 Jeep Liberty, Blue-Ox Adventa..