The DRAIN ROD was a success. I put it down the floor drain, and worked it back and forth, for about 10 feet down the pipe, and it opened up the clog! That's the good news.
The bad news, is after the water drained away, i saw a small chunk of debris in the opening of the floor drain. It was at the entry to the floor drain, in the section of pipe coming from the kitchen drain line. I managed to poke it with a piece of steel molding, and get it into the bottom of the floor drain. It was too big to pull out. I did manage to tap it with the piece of steel molding, and break a small piece of it off the larger chunk, and sucked that small piece out with a shop vac.
I'm not sure what it is, but there are picture at the link I've inserted. It almost looks like a piece of red brick!
I put the hose down the PVC wye clean out, and the water flowed through the floor drain, to the main. I could see the water flowing past the chunk of debris, so I might be ok to leave it in there. (SO, the kitchen drain line DOES go through the floor drain, which goes to the main drain!)
I am brainstorming ideas of how to either break it up, and vacuum it out, but I don't want to bang too hard on the debris through the floor drain, as I don't want to risk braking the pipe at the bottom of the floor drain.
Or, maybe use something to reach down from the PVC wye and try and pull it out. It appears to be about 3 inches in diameter. (Maybe something like a small fish net taped to the end of the sewer rod?)
Any ideas?
BTW, now that I can see the bottom it appears to be material that looks like it is 'dotted' - like a black and orange color mix. That does not seem like cast iron, does it? A few of the pictures at the link sort of show the texture of the bottom of the drain pipe.
I am also thinking of taping the endoscope camera to the drain rod, and putting it down the pipes and see what is going on in there, Maybe now that the water is out - I can see some clearer images?
There are two videos among the still pictures, at the google photos link below. I've also inserted a blow up of the picture with the debris in the drain pipe, and another one showing the 'mottled' substrate of the drain pipe, showing the spotted texture (maybe it's orange and black, or orange and white colors?) - not sure that is cast iron pipe?
https://photos.app.goo.gl/baKpnDnRBJmnTUfr7