I have listed things that in my words have oppositions with your play style
1. that you can use illusion spells, why should you use it, are you a mage, using illusion renders you completely unexperienced with sneaking, I mean really, you have sneak, if you use illusion you are completely out of your mind, however it does not mean to limit you to use invisibility powers, like the nocturnal agent power and the shadow stone, so you are supposed to use calm and then assassinate, that isn't even assassination nor reasonable
2. Choose either light or heavy armor, light armor should be chosen, sneak is 30% useless if you wear heavy
3. Why use speech, it doesn't have any importance to being an assassin
4. Archery should be used, it's also part of being an assassin, not just daggers (and swords)
5. Heavy Armor shouldn't be used, completely makes sneaking useless
However, you should know that these things are completely some facts about assassin-like characters, it doesn't mean that it IS how I said it here. Still though, I think that you should completely ignore magic, heavy armor, speech, lockpicking and pickpocket.