Interesting that it "wouldn't start" without starting fluid. I know from experience that my '83 240D will start at temps above freezing without the glowplugs. It won't like it but it'll start. Grind on that starter for 20-30 seconds and she should go.

Have you ever replaced the glowplugs? I'm a shotgun man in this respect, I'd replace all the glowplugs and the fuse right now. Better to do it now while its warm out than in Feb at -20F... I'll be replacing all the glowplugs in my 240D this weekend.