Shower floor cracking
I went to my local hardware store and tried to find some options. I originally attempted an epoxy coat, but it did like was mentioned and quickly came loose and fell off because of the flexible base underneath. I then went back to try something else. I saw this stand for "Fiber Fix" and they had one called 'Rigid Patch' which goes on soft and hardens "like steel" in UV light in about 10 minutes. Completely waterproof and shown to patch canoes, wheelbarrows, water tanks, etc. I figured it was one of those typical as seen on TV items, but it was on sell and cheap so I figured it was worth trying if it did what it says it can.

http://www.fiberfix.com/products/

They come in a black pouch with a clear film on it. They provide gloves and sandpaper as well for working with it. It's almost like a fabric when you get it out and is black on one side and gold on the other. The black side is what sticks and the gold fades away to clear when it's dry. You basically place it down on a dry, clean surface and then almost like massage it on from the edges in. The bottom black is gooey feeling and so is the gold underneath of the clear plastic. You try to smooth it on so that there aren't any air bubbles and get a complete seal around the outside. Let it sit in the sun for 10-15 minutes (or UV light in general) and it'll harden and the gold will disappear when it's done. I also noticed that it gets slightly hot itself while drying. My frosted shower door is between the base and the nearest window and this window isn't on the sunny side of the house, but it was still done in about that 10 minute time. After it's dry, you peel up the clear plastic from it and it's good to go. It feels like a fabric when putting it on, but is smooth like plastic when done. It completely sealed on around the edges, covered the holes, and actually has attached itself so tightly to the base that it doesn't really have any give where I placed the two patches.

To finish it off, I coated most of the shower base in Flex Seal. I'd never used it either and wasn't sure about it, but it also seems to work great. It does give more of a rubbery feel to everything and it takes a day to cure, but it seems like it worked.