This is very similar to an emergency that I had in 2010. This time, instead of IMC, it was a cloudy night and we were over coastal Florida above a swampy area with no lights. Like this case, the engine was still running, but not well enough to stay airborne; we could just "stretch the glide".
There were two airports within range. One was larger, and 13 miles away, but across a wide bay. The other was on the same bit of albeit swampy land that we were over, but unattended; and the pilot controlled lighting wasn't working. It was not near any lighted areas, either, so a real black hole. We made the decision to go for the further field, but it became clear immediately that we were unlikely to make it,
So, the small unlit field it was. We used the KLN94 GPS to draw an OBS line through the airport icon, centered on it, and rotated it to the runway heading. Then, using the GPS on full zoom we flew a DIY instrument approach using the OBS line as a localizer and the altimeter as a glideslope.
The aircraft's landing light picked out the runway centreline at about 10ft. We landed safely.