I'm sorry you haven't received any repsonses yet. I used to have that scanner as well. Apparently they've fixed the software interface because they used to let you select ICE for B&W but the scans would come out as two tone black and white images. At least they don't let you select it now.
Anyway, I always had better results scanning in RGB for B&W so I think your approach is the wise one. You can convert to greyscale later if need be and with the 14 bits of RGB info you're getting more detail in your scans anyway.
I don't know why turning on ICe gives you bad scans. Could you post a sample with and without ICE so I can see what you mean? If your negs are clean it doesn't usually hurt turning it off as it saves scan time anyway. A little healing work in Ps takes care of that.
Summary: Scan in RGB even when B&W. I don't know why ICE is giving you bad results. At worse, it just softens the image slighly (but not nearly like GEM does).