Payless is great and they carry size 12, and in some stores even 13. Its hit or miss though, so I go often to get the cute shoes I like! I'm a 12 BTW.
Maurices is a great store and they carry a Plus line of clothing. They have great casual wear, and their professional attire is spot on! AND they carry long sizes!!!
I know express carries up to size 14, although they are a little pricey, you can get great coupons online though!
As for the insecurities, for all you and your wife know the security guard is an a closet x-dresser, or transman and just wanted to talk or say hello. I've also learned that people are genuinely curious when they see me, and they really have no ill intention towards us, they just don't know HOW or what to say.
We all, even non-trans people, go though stages of development. Going through puberty as your wanted gender is tough. Going through puberty towards your goal gender entails the same process.
It just takes time. I know sounds easy, but its really important to remember.
Wishing you all the Best!