Tile pattern for shower base using large porcelain format
I think you're being too hard on yourself. So far, I think it looks great. Keep in mind that once you start setting the tiles in Thinset a lot of those uneven pieces will be OK. You'll also have uniform grout lines. If you start at the drain and work outward setting all the large tiles first, you'll be fine. You'll still have to cut or trim some of the tiles as you set them but that's to be expected. Your last tile on the lower right should be cut to match the one on the other side. Definitely think about using epoxy grout on this as it's much stronger. Smooth over those outside corners.
Also think about putting two coats of RedGard on all your wall surfaces in the shower.