I’m not the original developper of this core neither the orignal developper of p-uae.
As I said, I only added m3u and direct launch of games and fixed the windows build.
But I will try to help if I can.
Non native resolution (try to use scaleFX, then you will recognize that scaling is not working with shaders)
Yes, the core seems to have problems with resolutions under 640x400. So it seems to double everything. However you can try a different resolution within the cores options.
Mouse and Keyboard Keys cannot be mapped to a controller (DosBox is doing a great approach for that)
Yes, good idea. We will see if a dev want to do that.
Absolute Path Detection (games have to be in the retroarch folder to be played)
I have not that problem and I only use absolute path.
Here is an example of a .uae file I use :
I can try to see what is wrong if you post your logs at least.
It seems IPF Files cannot be loaded.
Many emulators needs a plugin to handle ipf files. Don’t know for p-uae. Never tried.
If those problems are deal breakers, sorry but you will have to use another better supported emu (WinUAE, FS-UAE). There is nothing better in RetroArch for the moment.
At least, now that it launch games, new bug can be found