So you messed with the old Picasso software (?) which is totally incompatible with Picasso96...Now you should get rid of everything what it installed.
I think that is a bit harsh.
Picasso96 should work great for your board; a clean install may work best, but that takes deleting the Monitor file and the Devs:Picassosettings file. A full install of Picasso96 (the last version is something like 2.1c) will have a guide for checking the board and settings after "setup" and before the "reboot" to select ScreenMode. Just Google Picasso96 ver 2.1c or whatever it really is. At least you will have the latest files. There is help file on AmiBay about selecting resolutions you might want. Then reinstall slowly checking the locations.
I am afraid that I haven't done the install in OS 3.1 in many years, but have done a dozen times this year in 3.9 (in OS 4.1 one only needs P96 for non-VESA modes). Searching Aminet you will find programs similar to LoadMonDrvs, since H&p copied one of those to use in OS 3.9 -- it makes for easier code to read and understand.
Post back when you have researched those things