1. Can I change my wifes clothes?

2. Can I acquire that sixy waitress getup and equip it to them?

3. Easiest way to level alchemy?

PS: I'm on Xbox.

Alchemy levels more quickly the more expensive the final product is. Try and make as many multi-effect potions as you can, and you will level up fairly quickly.

for alchemy, easiest way to lvl it up is mixing giants toes with wheat, it creates a potion that fortifies health and even with low alchemy, it should be worth around 600 gold at lvl 16-20 alchemy, and worth considerably more at higher lvls, also if you have enchanting at 100 make the following with fortify alchemy on them,

1 ring
1 necklace
1 circlet (only use a circlet because this is the only piece that can also be used with a falmer helmet)
1 Gloves
1 falmer Helmet/headdress,

that will give you an extra 25% magnitude to your potions per piece of clothing so in total an extra 125% on potions, i have these and my potions i make with giants toes and wheat are worth 2400 each im lvl 63 alchemy and i lvl up by maing 2 potions, its easy.

yes you can change your wifes clothes but only if she is also a follower, and about the maids cothes probably if you kill a maid and take them.

if you can get your pickpocket skill up to 100 and choose the top perk then you can take your clothes off your wife and she will be in her underwear. however she wont put anything else on and will spawn her old clothes on again at a later date.