Unable to remove display assembly

I tried to reproduce your situation to see if I could remove the front panel assembly without using a suction cup. I was able to open the phone by prying in the narrow gap filled by the gasket between the metal bezel and the bottom edge of the front panel assembly. Plastic opening tools were not up to the task, but the pointed end of a metal spudger did the trick. An iSesamo would probably work well too. Any metal tool with a thin and flexible enough end might work but I would avoid knives or razor blades. These are brittle and may snap, flinging sharp nasty bits into your eyes. Use caution when poking and prying as there are tiny electronic components on the dock connector close to the bottom edge. The left edge of the photo for step 12 of this guide shows the components to avoid. Wear safety glasses and be aware that the front panel assembly edge gasket will be badly damaged.