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Have you any photos showing the area from which you removed the KerdiFlex from the Kerdi on your curb? If the thinset mortar had cured for an entire day before this removal, I'm very skeptical that your remaining surface would be sufficiently clean to make a watertight bond with the KerdiBand.
Are you actually using KerdiFlex rather than KerdiBand?
I'm not sure I understand what plastic you removed. This was just a protective plastic on the steel drain?
And what effect would that have on the bond between your KerdiFlex and your curb? What am I missing here?
[Edit] I gotta agree with Mike about that floor. That scares me and I'm usually neigh onto fearless!

And keep in mind that the tile of whatever size has nothing at all to do with the waterproofing of your shower. That's just a decorative and protective covering for the waterproofing layer.
My opinion; worth price charged.