Can't take the rear panel off

Assuming you are using the correct screwdriver, you could try to take the screws out with the charging port facing downwards, so gravity can help. Even if you only get the screw out a bit, you could try to add tension between the screw and the frame with a very thin object. If all of that doesn't work or is too much of a hassle, you could always just break the glass and pry it off, but I wouldn't recommend it. More as a last resort.