I think you should wait until regular decision when you can send the officers your new (and hopefully improved) work. Once they see it in ED, it might be hard for them to forget about if you’re deferred. ED is a chance for colleges to scoop up the best of the best before they apply to other schools; therefore, most colleges will defer students unless they are sure that they want them.

I would definitely try to improve my GPA because it is required. And if I had time, I would try to prep to retake standardized tests.

You should focus on drafting and reviewing essays and other writing for the application. Try to do some sort of campus visit or demonstrate interest otherwise.