That second video is very impressive Ayrton.
Is the handle being wider at one end the reason for the squint sprocket? If so, try putting a spacer (a couple of washers or a piece of material with a suitably sized hole in it) between the sprocket and the narrower part of the handle to fill up the space. This should make your sprocket straighter and hopefully reduce the chance of the chain jamming and/or coming off.
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