Bonecross

You might want to experiment with diluting a bit of saddle soap into a jar of water and use this to prepare the leather. I find that leather carves and cuts more easily but it might not be necessary

There are different ways to use antiques, but usually they are useful to get into crevices. (you wipe off the raised areas so it stays in the tooling). I do however love doing a base of light brown dye then once dry I'll pass over the entire surface with mahogany antiquing paste. The application method is important, and so is removing the surplus almost immediately. So you can highlight tooling and natural flaws in the leather with it, or sort of "tint" the leather. If you are expecting it to act like a penetrating dye, you might be better off with liquid dye. I also want to note that each time I use a black antiquing paste, it streaks like you show.

One more thing Mystery braids! But that bracelet you show is not super complex, it's actually just cut perpendicular strips and then they weaved in a lace strap of equal width to the slits down the middle.

Making simple stamped keychains are also fun and easy, plus you can use scraps from other projects. You just need to pick up a bunch of stainless steel keyrings, rivets or eyelets. Many design possibilities, even some that pull double-duty as deployable iPhone stands/holders.

Oh my... I've never worked with hair on hide... but dang you've sold me! I just wanna pet it

You are right to be wary of placement! The best way to learn is to make mistakes though, so be bold... And maybe make a jig to help align the pieces Usually I sorta curve the top belt leather and guide it along with my fingers as it gets laid down, like laying a transatlantic cable! If you make a sound like a machine it helps You will need to sand it anyway, so maybe make one piece slightly larger and then the edges don't need to be perfectly aligned. You can clean it up after.

For me, nothing beats a self healing mat. The feeling as I draw the knife is superior. They do need to be replaced every so often though. I find deals on Amazon sometimes.

That's really impressive for a first project!