"Tomorrow" took a while to happen, but day 3 of the build saw me finish the planking, filling, and sanding. Despite not being as nice as it could be, it no longer causes internal pain by just looking at it. I've also watched and read enough guides on planking to know that the instructions that came with the kit are not ordered in the most optimal manner, so I've jumped ahead and installed the keel.
Next step is to install the final upper plank (and cut in the oarlocks), then trim the excess from the planks at the stern and get started with the outer planking. I will be attempting to do that layer properly and fortunately I seem to have found a video build guide for this exact boat kit.
P.S. I realize now that I have so much extra wood that starting over would have been viable. I'm shocked at how much extra wood comes with these kits - I almost have enough to start over even now after finishing the planking!
However, I would rather have extra planks for a future project than mess up during the redo and not have enough to finish this model.