gtk or any other mapeditor can decomplie without having some problems with the map,,,, lol,,,,
some textures r not fit or just not looks like they do in the orginal!
and as u said lights, misc, values and other maybe wrong,,,,,
so just try to remake it,,,,
i just use decomplie to look how to make some stuff and/or make som perfabs of it,,,,,
but if u r looking after perfabs then look here