Nice Job Tony! I recommend that you clamp your vice when doing delicate work like this, as it will eliminate one more variable that your skills will not have to cope with, allowing your fine motor control even more precision.

Buy a pre-dimensioned and slotted bone nut for your guitar (Strat or LP, etc.) and leave bone nut making to a luthier. Most players just want a NuBone or bone nut and can sand it and glue it in neatly with care and learn in the process.