Good news: it works now! I opened Omerta up in WinRAR. I decided, after looking at sprites, to instead look into the decorate folder and edit the pickups txt. I just deleted the armor text, and that solved it. The side effect of this is the armor is now just vanilla doom armor, but I can live with that.
In a roundabout way, doing all this made Slade make sense to me now.
Thanks again, Cosmobyte, for replying and helping me out. Now I can enjoy being a funny mobster against Kriegsland enemies.