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First of all that was way too long to watch. We know what's going to happen, no need for us to wait through the whole thing. I have no experience with twixtor. Where did you even get it? I searched and I can't find any downloads or info.
The easiest method would be to do the time remapping using Twixtor in AE. You would need to roto your legs, and use the mask as a motion source. If you only have Twixtor for PPro, you can roto your legs in AE or some other compositing program, export a matte (white on black should be fine), and use that in PPro as an Alt Motion Source or FG Matte. You could also try tracking your legs in Premiere with the Twixtor Track Points, but I've never really had any luck going that route.