It's about the same temp here in the frozen north country, and my '76 is cold starting OK- a little more hesitant, but still OK.

While cranking on ether, did the engine even bark or cough?

If glow plug light is intermittant, probably because the relay is intermittant, so glow plugs may not be working at all. In fact, if plugs were working and the ether got in, I think you'd get quite a bang out of your engine!