Motivation for Schoolwork and Chores

We are constantly looking for ways to motivate our ds to do schoolwork and chores and to follow the rules. Here is what we have come up with. If ds is finished with his schoolwork by 4PM and he has an average of an 80% for all assignment he will receive 1 hour of screen time. If he comes to me before 4PM and says he is done and I have to remind him about an assignment I take away 15 minutes of screen time. 2 reminders costs him 30 minutes. I give him poker chips that he can redeem at any time (only after schoolwork and chores are finished) throughout the week. I can use them daily, or save them up to be used on one day for an extended video game period. It is his choice.

We are having a bit more trouble with the chore part, though. We currently give him $10 per week for allowance as he more opportunities now to do things with the youth group. Monday he has pooper scooper, straighten his room and kitchen duty, Tuesday he weed eats the yard (it is small so it takes him about 15 minutes), straightens his room and wipes down the bathroom, Wednesday he sweeps the porch and lanai, dusts upstairs, has kitchen duty and straightens his room, Thursday he deep cleans the bathroom, straightens his room and washes his laundry, Friday he has kitchen duty and Saturday he dusts and vacuums his room. Each day's chores should take him no more than 30 minutes, except the day he deep cleans the bathroom. After adding all the chores up he has a total of 15 chores. $10 divided by 15 gives me .66. I think I might make each chore worth $1 and just not pay him for straightening his room, giving me a total of 11 paid chores.

So how do you decide what to pay for? Do I pay him for the completed job, even if it took him 5 times to get it right? Do I deduct money for each time I need to go back because it was not done right the first time? Do I give him a specified number of times to get it right and then withhold the money if he goes over?