Unfortunately I have to play Doom without OpenGl these days because my laptop has palpitations if I try using it on Doom maps as complex as these. On the other hand it means I can spot all the software mode related problems.
Something that came to my attention were these strange graphical artifacts.
At first I thought they were slime trails, a problem inherent to the software renderer, but it actually seem to be a dummy-sector outside the map that bleeds through the walls at certain angles. Why it is doing this I cannot say but it looks very bad. Also note the armour bonus that appears to be hovering in mid-air in the second shot, as if it thinks it is inside another sector with a different floor height. Perhaps this is the result of an unclosed sector or node error?