You can certainly use PF for making PC builds. Just compile it using VC6 or higher, and link the PocketFrog_x86 library in your game. Additionally, you can change the resolution of the PF app to be anything you want. (You'll see it hard-coded as 240x320 in PocketFrog's game.cpp file.) What I did was add "width" and "height" variables to the m_config struct, and then set them during the game's initialization. Note that that only affects the PC build and as far as I know, there's no way to do full screen with it on PC. Once you're done developing/testing your game on PC, just compile it using eVC and link to the PPC libraries.
For the RGB565 images, PocketFrog converts the images when they're loaded, so it doesn't matter what they were to begin with.
For sound, I use the FMOD library, which is quite powerful and relatively cheap for hobbyists (and free to develop with). It includes compiled libraries for PC and PPC builds. But you can also use Hekkus or MikMod, which are both free.
Also, I've looked at Allegro, and it's actually really nice for PC game development. It'll let you go full screen at any resolution, and it comes with lots of classes you can utilize.