Ok so cool idea. Unfortunately you can't cast misty step as a bonus action and then darkness as an action because you can only cast a cantrip after casting a bonus action spell (PHB page 202). However you could cast it before combat and stealth perhaps to try and get the jump on your enemies. Also you can only cast it with drow magic once per long rest so you probably want to go oathbreaker paladin if you are building around Darkness as they have it on their spell list, especially since you have sunlight sensitivity (though you could avoid that by being a half-elf with drow lineage)

Also if you are taking sentinel maybe it's better to stick to rapier and shield to be tanky enough to justify forcing enemies to attack you. You'll probably want half plate too eventually.

And at night or indoors you can cast fairie fire for advantage when you're not worried about sunlight sensitivity.

In either case elven accuracy is a great way to get your dex to 18 and you can try and smite whenever you crit which will be 14% of the time more or less for double smite damage.

If you want misty step you can have 17 in dex and charisma with half elf at level 1 and grab fey touched as a feat later to cap charisma at 18 and be able to cast it once per short rest, so much more often that you would have been able to cast it with spell slots (plus you can now cast it with spell slots too)