In the compatibility tab, if you check the option to disable display scaling at high DPI, does that make a difference with the main menu being cut off?
Try rebooting your computer. If I leave mine on long enough, eventually I'll get a similar issue (black textures and rainbow highlights indoors and at night) until I reboot (though it can also eventually go away on its own, as well).
Does it make a difference if you switch to Software mode in the configuration program? You can start the program from the install folder (..\SteamApps\common\divine_divinity), or in the Steam library, right click DD and select configure.
Try the
Windows 8 Performance "Patch" (works in Win 7 and 10, as well)
In the Divine Divinity install folder, edit the config.div file (in Notepad, or other text editor) and add/edit the line
rgb 555 and change the number to something else, like 565. If the line isn't there, go into the graphics options and change the gamma, or something, and it should be added, or you can do so manually (just not as the last line in the file, as the game expects that line to be blank, and ignores it).
You can try using the disk version of the configuration program, to set the game to run in Direct Draw mode. Rename or move the existing configtool.exe and NlsEng.dll files in the install folder, and extract the disk versions from
this zip file.
Note that this will reset the game resolution to what the disk version supported, but you can manually change it back by editing the config.div file.
Maybe WineD3D will work better than Direct3D
http://www.gog.com/forum/divinity_series/windows_8_slow_graphics_problem_fixed_using_wined3dThere may be some other suggestions you have not tried yet in the topics/discussions below.
Software/Direct 3D IssuesGraphical Issue, Indoor textures turning black?