Nice work Dan, I really like the finish youve achieved. A couple of thoughts_ that endgrain on the top horn: it’s just how wood is sometimes, you can grain fill , clear fill or both. Bits of timber that dont take up stain: happens when you get different harnesses and grain tightness in the same pice, it’s a pain. One option that can work is sanding the harder section with a slightly rougher grade of paper.
Nice job