1) For the Yahoo Finance part.... well, you got me. The app is not really a yahoo finance client, it just uses information from Yahoo. But for the limited time I tried, I couldn't find an explicit way to retrieve portfolio data from Yahoo. I am not sure if it can be done..., but I do find YQL might be the way to go. I will change the title to make it clear : p
2) That's a good idea. The app currently automatically re-sign in if the username or pwd changed. That indeed can be confusing. I will add signin and signout buttons.
3) No, those info should be displayed by default, but unfortunately for (some) mutual funds and indexes, Yahoo returns nothing for the ask/bid price. In short, if you still see '-' after a couple of refreshes, it means the data are not available from Yahoo.