Since you didn't receive a 1099-S,
Proceeds will be Sale Price minus Commissions: $800,000 - $66,469 = $733,531
Total amount paid will be Purchase Price + Improvements: $340,000 + $126,500 = $466,500
That's it. The sales commissions are covered in the proceeds, so don't check the 'Additional sales expenses' on the next page, check 'None of these apply'. This section is when you have a 1099-S that doesn't reflect the sales expenses.
You don't itemize your improvement expenses anywhere.
