Hey all I just picked up Baldur's Gate: EE and had the same issues as above. Looks like the menus don't like UW resolutions and will be massively off center (despite being, as far as I can tell, the correct resolution). I tried changing the Baldur.ini file to match 3440x1440 but it didn't change anything. I got the game to work eventually, at least getting my character created and to the game where I can control it, where it does appear to correctly support 3440x1440 and looks pretty good too.
THE FIX: Basically you have to go into windowed mode for menus or anything else that doesn't work right. Old-school ALT+ENTER will toggle you between windowed and fullscreen mode. Once you get to the game you can play in fullscreen, at least for as much as I tested. Going back to play it now and if it bones up at all I'll let you all know