I know you are taking Kaplan for the DAT, but you are also planning to use Destroyer, Cliffs, Feralis, and other resources. This may be too much considering Kaplan has its own diagnostics, workshops, exams, and quizzes. If I were you I would definitely use the other resources like Destroyer, Chads, Cliffs, Feralis, Bootcamp, etc, but I don't know how you would use that stuff with Kaplan.
I took the Kaplan class early last year and if I were to use the material I am using now to study for the DAT back then when I was studying with Kaplan alone, then it would be a huge mess for me because I would be studying from multiple things and it would be somewhat out of place for me. It would be nice to get as much practice as possible. Most of the forums say that the resources I listed above are best. Kaplan is good too, but I hope you can be able to manage everything you plan to do in the given time before your test date because some things take a while to do (i.e. Destroyer for Math, some of Kaplans workshops for Math, Destroyer, etc). I think you will be fine though. Good Luck!