6 months should be more than enough to do that. In fact, you can study for DAT (1 month), take it, have the DAT score sent to the schools (1.5 months), prepare your AADSAS application (3 months), have the AADSAS application processed and sent to the schools (2 months), within 6 months.
Definitely. My personal view is that anything beyond a month of studying will yield sharply diminishing returns--IF you've already had the material in class. Most DAT studying will hopefully be simple review, which doesn't take nearly as long as learning it the first time did. Good luck!
FWIW, I disagree here (about needing only 1 month to study the DAT). I just don't think it is enough time. Bill mentioned one month would be enough if you already had taken the coursework. I'd would add that you would have had to have been a very good student as well...but regardless, I'd still recommend more than a month...something like 3 months with intensive studying in the last month. Even if your core reading and math skills are up to par, I think it wouldn't hurt a person to continue to memorize OChem and Bio, habitualize solving problems in the natural sciences, and practice PAT problems.
One last thing, I did want to mention that it also depends on what your goals are (in terms of what DAT score you are shooting for).