If you click your name at the top-right of the page, you should see your active sales. If you click Edit Sale, you can toggle between Active/Inactive. If it's Inactive, it doesn't show on the For Sale page, and no-one can buy it. I need to improve this bit
I've just added a Refund button, it's on the Sell Orders page. If you click it, a Money Button appears so you can send back the amount they paid. And it'll mark the order as Refunded.
Not that I know of at the minute. I think Money Button are working on this. The app doesn't store tokens held or balances, everything displayed is direct from the API. I'll be adding new features as they become available though.
Once you've defined the token, you should see it in a list here: https://bitcointoken.exchange/tokens/ , there should be a Mint button on the right which takes you to a page where you can create the minting transaction. After that, it'll show in My Tokens