Y-you can craft jewelry with smithing? I had no idea! But how? Is there any particular type of jewelry I should try and make for myself, and for profit?
When you go to a blacksmith's forge/anvil, there is a category for "Jewelry." If you are holding any Silver or Gold Ingots, you can craft necklaces and rings. If you are also holding any gems (amethysts, diamonds, etc.), you can craft even more valuable items. The higher value of the item you create, the more it improves your Smithing skill. (Edit to add: Don't forget that you need to turn gold ore into gold ingots before you can smith with it. You can do that at a smelter, which sits near the forges in Whiterun, Dawnstar, Markarth, and perhaps others I'm blanking on.)
My advice: Clear out Kolskeggr Mine (just north of Markarth) and mine the hell out of it. This will give you a ton of gold to turn into jewelry. Also hold onto any iron ore you find, as you can use the Transmute spell to turn it into gold or silver ore, which can then be made into jewelry as well. (If you don't have it, Transmute is in Halted Stream camp, northwest of Whiterun.)
What perk would that be? Also, what are the practical applications to using Quiet Casting, Calm, and Pacify for a thief? Even without Quiet Casting, I never have noticed myself being heard casting illusion spells before near enemies. I've tried using Calm before on people I failed to pickpocket, but as soon as the spell wears off, they remember my crime, and call the guards. Lastly, my illusion is not high enough to get pacify I don't think. What does that do?
Oh, the first perk on Illusion's middle tree (I forget what it's called) boosts the level of enemies you can affect with Calm spells. Combined with Kindred Mage and Animage (the prerequisites for Quiet Casting), this will let you cast Calm (or Pacify) on most enemies in the game. If you want to Calm guards too (who reach pretty high levels with you), you might also need Illusion Dual Casting in the long run. (Pacify is the same effect as Calm, but it affects higher-level enemies.)
And yeah, it's only a temporary effect, so you still need to deal with guards eventually. Fortunately, with Thieves Guild membership or Speech perks, you can get away with pretty much anything by bribing guards.
Edit to add: Oh, I forgot to answer "what are the practical applications..." Well, I definitely get noticed casting spells around enemies without the Quiet Casting perk, so maybe you're just more careful than I am. The most useful effect for a thief is using the Aura Whisper shout, which shows you the locations of all nearby enemies without alerting them to your presence. If you use it without this perk and anybody's in the room, it will probably go from hidden status to "bad guys looking for you" status (but not detected, necessarily). If you ever get tired of mixing invisibility potions, it's also nice to be able to cast Invisibility silently.