Whats your gpa? Why would you wait until Aug to submit app when it seems like you are ready for the DAT once you get confidence. I didn't have confidence until the week of the DAT when I started taking topscore, but I didn't have achiever to compare to. I don't think you should wait so long to submit unless you have a low GPA and are banking on a heavy science 4.0 semester. Get a sample ADA, keep going through topscore, and kill it. It seems like you're on track to at least do well above average so just keep on trucking. Make sure your LORs are ready, or near ready, kill that DAT, and get that app in.
It feels so good once you're finally done. When I was studying I thought I'd be lucky to get a 19. I took topscore and got AA 20, 22, 22 and similar on the sample ADA. I'd taken so many practice tests and knew not to get bogged down by tricky problems. I managed my time fairly well and came back to marked problems, even changing a few on bio. Once I finished the last problem on the actual DAT and rushed through the survey using the hot keys, it took a few seconds and displayed my scores. I just looked up and down the list and saw all numbers that were fairly reasonable and I was pleasantly surprised. I never would have thought when i first started studying for the dat that I'd pull a 21.