Law / Polish Visa questions - will they let me back into the country? [8]

I am an american and have been living in Poland since April 2011 (5 months). I have been applying for my visa in poland. I have not completed all the requirements and will surely be denied on the 12th of september when they make the final decision. I am leaving for the states on the 14th of september and will try to return in one month-- will they let me back into the country?? I am flying from USA to London to Poland, which leg of the trip would they stop me on if they arent going to let me back into Poland. Will I have any problems leaving the country on the 14th? What happens if i try to return and they do not let me in? After you are denied a visa is there any way to appeal?

I know this is alot of questions but I am trying to figure out, so thank you for your time and your responses.

Travel / Overstay in Poland (banned from entering Shengen for a few years?) [8]

My company has sent me to Poland to work. I did my job and overstayed the 90 out of 180 days by about 2 months. I am hoping that when I leave through the airport in Warsaw to go back to USA that I will be banned from entering Shengen for a period of a few years, this way my company cannot send me back to Poland.

Will they check my passport when I try to leave the Warsaw airport to fly home?
Is it very likely they will tell me not to return or give me the stamp that says I overstayed?

I love Poland and mean no disrespect by asking these questions, but it is very hard on me to stay this far from my family for months at a time - especially doing a job that I hate.