For the love of all that is good, don't do this for anything beyond random hobbyist screwing around. A Dropbox compromise shouldn't risk your entire company's server infrastructure.
> If you only have need for one free tier instance leave it running.
No, because the 750 hours/month can be used by more than one instance. You could, for example, try out database clustering by running two t1.micro instances for two weeks.
> Finally resist the urge to use your GUI when working with your project even when your working with your project on a local machine you’ll find that as you move along with your project you’ll be in better control of the project when it’s on the remote server.
The AWS Console is perfectly usable for 99% of what you'll need to do. Most users won't need anything beyond it.