So, I'm actually not sure if I have fixed my problem, for couple of reasons.

1) The handle unscrews from the diverter assembly by putting it in the filter position. Then there's access to the screw.

2) I bought the whole diverter, since I couldn't find just the spider gasket. The gasket comes glued into the diverter, but I was told to "lube it" like an O-ring.

Now... virtually nothing has changed. I still have dirt in the pool - no more or less than ever. I do have 1 tree near the pool, and our neighborhood is like a squirrel resort - so maybe it's just the squirrels knocking stuf into the pool from the tree.

BUT - I'm still kind of getting water out of my backwash hose in Filter mode... but if I take the backwash hose & bend it at a right angel to the ground (pointing up at the sky) it only seems to fill up to the level of the pipes running out from the pump to the pool. I'm surmising that it's because my pool level is higher than the pump.

That's where I'm at...

Thanks for te welcoming greeting.
-Rob