Tom listed a perfectly ideal situation as far as completing the necessary credits. If you don't want to attend a summer session of school, then you certainly could take 14 credits each of the next two semesters. 14 is still fairly lax (okay, I find it extremely easy), and should allow plenty of time for studying.
The bigger problem in what you are proposing is that you say you will take the DAT by the end of the year. Do you mean by the end of Dec.? That simply won't cut it with the application cycle. Most schools will have classes 50% full by the time schools receive your DAT scores, and as it is right now, if you were to mail in your AADSAS application, schools wouldn't get it until the beginning of November. Secondaries and interviews would be pushed too far back to be extremely competitive.
In my opinion, you could get acceptance at a school or two, but they may not be at the schools you really desire to attend, and acceptances may not come at all.
Bottom line: you can EASILY graduate by next summer. Given that, go ahead and apply, but plan on taking your DAT within the next 30 days. This will DRASTICALLY improve your application and chances of acceptance. Trust me on this one. Waiting any longer than Oct. 11 to take the DAT will simply ruin many of your chances to be competitive.