A MD80 Captain failed to Go Around IMC when his aircraft remained unstabilized below 1;000' to landing.

Narrative

I was pilot not flying monitoring the Captain's ILS approach. The weather at the airport was approximately a 400 FT overcast ceiling and 1 mile visibility with fog and rain. During the approach; the Captain unsuccessfully attempted to arm and re-arm the ILS approach several times. I observed localizer deviations up to and including full scale deflection while the Captain 'chased' the localizer using heading select. Inside the final approach fix; not established on the localizer; the Captain also began his descent using vertical speed. I called for a 'go-around.' In all; I made four separate go-around calls inside final approach fix. The third time was at 700 FT; when I also informed him we were not on the localizer and he was inside 1000 FT not configured for landing. He was unaware we were still at flaps 15. The Captain elected to continue the approach and descent; in IMC conditions and subsequently land from an unstable approach just as I was about to take the controls. I believe this was a FOQA airplane.