Sorry to hear about your losses. You clearly have potential, given your major and GPA, so don't dispair. Though I never took a Kaplan course, I've read a lot of negative things on the DAT forum and would urge you away from this route; hundreds of people have used the exact resources you listed and done quite well.
It sounds like you need a really solid schedule to follow ("due dates") to keep you on track. I would check out jimmpannzee's breakdown- I liked the 3 week schedule he has posted. If you feel like you need more time, expand that schedule (ie, take 2 days to do what he has listed in 1) and repeat as needed. Best of luck on round two, you got this.