Thanks for continuing to help. A lot has happened since I last posted. I will attempt to summarize that here, maybe this will help some other poor schlub like me that comes up here with same problem.
I went back to both Loew's & Home Depot and tried to ask for suggestions. Most of what I got was a lot of conflicting or non-helpful advice, much of which did not even make sense, so I then went to a local ACE Hardware store. There at least you get someone who supposedly knows what they are talking about & can spend time with you. I explained my situation & showed the guy photos of my existing flange etc. He immediately went to the aisle and told me this was all that I needed:
http://ace.lvsprd1.gsipartners.com/product/index.jsp?productId=1272857
Now the versions of this product that they had came in a plastic bag with no instructions/picture like the one above which appears to show this fitting underneath the existing flange.
He told me it was best to put it underneath the flange but if I could not get underneath it to simply put it on top and screw it in using the existing screws already in the flange.
I asked him what about the size/diameter, would it work with all flanges & all toilets & he said yes no problem you just unscrew the pieces and move them together/apart and screw back together etc.
I tried first to get it underneath but that would not work, also I did not understand how even if I could get it underneath how the toilet bolts would then fit under there in the first place.
So I switched gears and mounted it on top of the broken flange. I was able to use 2 of the existing flange screws to tighten it down but the piece has another 2 holes as well so I decided to drill into the floor and anchor it there as well to keep it solid as possible.
I then luckily decided to make sure the toilet would fit over it b4 putting a wax ring over it and then putting the toilet on top of all that.
What I found was that the toilet would not fit over the kit above. I even tried completely removing the kit's screws that shape/hold it together so I could move the halves in as much as possible east to west direction since the issue appeared to be that the external diameter of the kit hung over the external diameter of the flange and the underside of the toilet has a ridge or whatever there that was hitting the outside of the kit making it impossible to have it sit around it. Even if putting the pieces together as much as possible it still hung over the ends like 1/4 of an inch on one side in north/south direction and I could only have the toilet sit either down on the front or down on the back.
I then did a lot of research both on web in general and youtube in particular over the course of I guess 2 weeks with whatever spare time I had.
Based on that I decided my only do-it-yourself options were either of these 2 options:
(1)
https://www.amazon.com/Toilet-Flange-Repair-Kit-Flanges/dp/B078HGCYY
OR
(2)
https://www.amazon.com/dp/B00KBBAN5K/?tag=skimlinks_replacement-20
I opted to try #1 above first and it arrived about a week ago. Yesterday/today were going to be my days to see if I could get that to fit/work but got derailed by a snowstorm yesterday and had to leave my car abandoned on the side of the road and walk home for about 7 miles. Today I was able to retrieve the car but am too exhausted to even think about lifting a finger to fight with this toilet again.
My next days off to try to look at this will be next Tuesday, assuming I am not too sick to even try it then (I feel awful now after my 6 hour odyssey through snow/sleet/freezing rain yesterday) and have to work friggin' three 12 hour shifts in a row Sat/Sun/Mon (probably too much information but that is what I am stuck in right now, about to just crawl into bed now actually to see if I can fight off what feels like a fever and some kind of flu/cold).
If the option #1 does not work (either the toilet doesn't fit over it or if it does fit but continues to leak or is not stable enough) I will then try #2.
If that does not work then I have to try to get a "professional" - hopefully not as bad as the 1st plumber who screwed all this up 2 years ago which I posted about in another thread - to try to remove/cut out the existing flange, hopefully not damage the existing pipe, add a new flange, reseat the toilet etc, all to the tune of probably aroun $1000, OR say screw it, try to find some kind of flange/pipe plug to seal it up, throw out the toilet, and put something over that mess like a big flowerpot so I can at least use that bathroom again for the shower & the sink.