In-ground vinyl lined pool, installed in 2009.

I had a leak, which was getting worse and worse. I bought dye and
figured out where the water was leaking - around the return fitting
installed on the side of my built-in plastic steps. When I unscrewed
the eyeball, the front part of the fitting came off, and I could see
that it was actually broken. Using the dye, I can see that water is
leaking around the remaining part of the fitting inside the steps.

This picture shows how the fitting looks (I believe) when brand new:

The piece in the top left corner is what is broken. The front part has broken away from the inside- and outside-threaded part.

This picture shows the rear of my broken fitting:

So, it appears that the double-threaded part is still secured by the
plastic nut seen in the top right of the first picture. I assume that
the two rubber gaskets should be inside and outside the steps, but there
is not one on the water side of the steps.

My questions are:

1. Should I try to unscrew the double-threaded part of the fitting still inside the return?
2. If so, how do I make it screw out? There is nothing to grab and turn other than the inside of the threads.
3. If I do get it unscrewed, will the washer and nut on the dry side of
the steps fall down into the dirt where I can't get to them?
4. Or should I caulk all around the opening, hopefully sealing up the leak?
5. What should I use as caulk?
6. If I do this, should I also use silicone or something to secure and
seal the flat part of the fitting onto the water side of the steps?

As a temporary fix until the swim season ends, I fabricated a temporary
gasket using a flat rubber sink stopper (I cut a hole out of the middle
and have it secured with the return eyeball). I think I'm still losing
water, but at a much slower rate than before.

Any and all help is appreciated.