I'm not sure I know how to answer all of your questions, but this might help.
ETF's in general require extra fee's to pay the people who create and manage them, in the example above this would be the Proshares people. Leveraged ETF's require higher fee's because the amount of time and energy people need to put into them is higher. This extra time is because they involve derivatives that need to be swapped out or managed daily. This is one of the reasons they are typically for day trading. The other reason is because if you can go up 2x faster, you can also go down 2x faster.

In your example, a lot can happen in 6 months and if 10% is your goal there are less volotile ways to go about trying to get it. Expense ratio is what it cost the fund to manage the ETF. Its like a business expense of the fund. There are unique expenses with ETF's that you obviously already know about, but I couldnt tell you specifically what they are. If you want to know how much you'll make you gotta know what those are and factor them in. Also, each fund is different.

$10,000 bought.
Falls to $8800
$10000 - $8800= $1200 loss
$1200 + $14 commission = $1214
$10000 - $1214 = $8786 Left in your Account, less whatever fees unique to the ETF you traded.

For the other one its a thousand dollar gain minus fourteen bucks and the ETF fee's, whatever they may be.