1.- Press right mouse button on the slider number, this one will start to blink, then set the number you want and press enter. Be in mind there is max and min values if you reach them will be set to their ones.
2.- I will have in mind. Or maybe just delete that action due runs on window you can always click on the close button of the window. Will see.
3.- Go to "Palette" tab in the leftbar. THen there is a "Palette" slider with all the retro palettes . CPC is number 3.
4.- The steps in erosion is how much iterations. Set intensity to 100 and play with step values and you will se perfectly what it does.
Btw, here is a Erosion text tutorial:
https://kronbits.itch.io/pixatool/devlog/14593/tutorial-pixatool-erosion-dilatio...
EDIT: Also in the Info tab you have some tips/Trick/Hotkeys