Thanks for updating us, I like the photo of the sanded chine. Really looks good.
I can't tell you how many things you wrote in this post that resonate with me and my build. When I began i thought it would take me a year. At that point my wife asked me how much longer? A year? I said "it better not". Two years later close but... love my fantasy world.
As for the Kilz primer, I believe the latex product is not workable in any case. The oil based product can be used with single part paints. Honestly, my knowledge is based only on what I have read, I have no first hand experience. I was going to use Kilz and rustoleum on a one design planing sailboat that I have until I realized that I can't get either of those products in the PRC. Going to end up with a $600 paint job on a $100 boat.
For your fillets, small lengths of pvc pipe make pulling and sanding them much easier. Pull the fillet with one size larger than you want and sand with the size your looking for. Wrap 36 or 50 grit sand paper around the pipe and get your rough shape. After it's close, skew the pipe out onto the flat surface, working both sides of the fillet to blend the radius without undercutting the fillet. Move to 80 before getting it fully blended so you have some room to clean it up.