Don't know specifics on what parts of the online app are being done incorrectly. What I should have said was be sure to follow the directions exactly and fill it out as completly as possible, so that there won't be any opportunity for them to kick it out.
As for the second question about pay. My understanding is that new hires at the academy are getting a nominal salary (someone at work said $8.50 per hour, that may be rumor, but I do know its not a lot....but you're also only talking about 10 weeks or so). However, you also get a tax-free per diem that will cover your living expenses out in OKC. There are several apartements (Walnut Gardens is one...and they have a web site - google it) that cater to the FAA only, and have fully-furnished/outfitted units, so all you will do is bring your clothes, computer, etc. They know the rate the FAA pays you and I can guarantee that the rent will be exactly what your given in per diem. But its still the best deal going out there. No lease, no ties, just pay while you stay.
Then as for pay...once you're at your first facility.....go look at the thread entitled ATC Benefits under the Air Traffic Header. The pay scales are posted (or link to the scales are), and an explanation on how to work them, within another post I made (if you have a speciofic question about a specific area or facility PM me and I will try to help). That thread also talks abouit some of the other benefits that come with the job.
As for location, on the app....I am told that the more locations you put down the better your chances are at getting an opportunity to interview, simply b/c more areas/hubs will have your name and test score on their rooster. So, if you're flexible about where you land, fill in all 10 (or however many spot there are).