Its all in the readme, .
For fullscreen, hold both triggers and select. That will set Auto-zoom.
Mouse Savestates is what you want, set your mouse to desired loaction on screen, then hold both triggers and triangle to bring up mouse savestate menu.
You could try also, altering speed of mouse. By default, triangle is normally toggles mouse slowdown.
I can seriously recommend keymapping the PSP's buttons for movement in Dungeon Master.
Thats the key config I use, its much easier to use the mouse pointer for spell casting, combat and opening doors and switches.
use the four PSP's direction buttons for step forward, back, left, right.
use the two PSP shoulder buttons for 90 degree turns left or right.
Dungeon Master is a little odd in the screen size department, I find this the best screensize in pspuae.
hope it helps make things easier for you.