Sorry i ment 17 (edited my first post and fixed that)
And yes my wisdom is high due to monk giving me bonus AC from it due to Unarmored Defense
So yeah I'm looking for advice on my last 3 levels (or more if someone can provide a good argument for not going all the way to 11 monk)
I've recently discovered something that might fit your build as well. You've got Ranger 3, so you're half-way there. Go to Ranger 4, grab the feat, then add Paladin 2. Ranger 4 and Paladin 2 combine to give you 6 spell slots with which to smite for a relatively small investment. Of course, adding Paladin makes it a very, very MAD build!
That would make your build in total: Shadow Monk 11 / Assassin 3 / Gloom Stalker 4 / Paladin 2.