1. Use SpriteX(sprite$) - OriginX and SpriteY(sprite$) - OriginY. This will give you the real position ON SCREEN of the sprite.
You can alternatively use SetSpriteFixed(sprite$, true). The sprite will always be on screen and the SpriteX and SpriteY will be real on screen values not altered by the OriginX and OriginY.
2. Flipping sprites... Mmm, I will check if it's possible. It would serve you well for the sprites animations hein?

3. PF is kinda strange on the desktop. The next version will apparently allow real desktop fullscreen and different resolutions. At this point there is not much I can do but I will give a look at the PF forums to see if it's feasible.