I think this ideas is really interesting, but I'm missing the forecast for the direction of the weekly high's and lows.
Currently all results of the challenge depends only on the weekly closing price,
So I would suggest a change to your idea for discussion:
Higher and lower highs and lower and higher lows lows could also be calculated for the results in the same way as the closing price is evaluated now:
1 point for the right direction, -1 point for the wrong direction, ranks for gold medal earns 3 points, silver 2, and bronze 1 point.
So for the forecast of the moves of the weekly high against last week's high there is a maximum of 4 points to earn and a maximum of 1 point to lose.
The same is for the weekly low: a maximum of 4 points to earn and a maximum of 1 point to lose.
To give the close price forecast more value, I would add 1 point to the direction and 1 point to the medal ranks, so it would be
2 points for the right direction, -2 points for the wrong direction of the closing price, ranks for gold medal earns 4 points, silver 3, and bronze 2 point.
So a maximum of 7 points could be earned with the correct forecast of the closing price, and a maximum of 4 points for each of the weekly high and low forecast. The maximum is 15 points per week if someone has all 1st ranks, and -4 points if all forecasts were wrong.
So, extending your example with this change, I could calculate the following results under the simplifying assumption that the ranks for predicting the lows and highs are the same as for predicting the closing price, and assuming that the direction of the highs and lows was correctly predicted:
weekly close: direction correct, 3rd rank: 2+2=4
weekly high: direction correct, 1st rank: 1+3=4
weekly low: direction correct, 5th rank: 1+0=1
total: 9 points.
If the directions were wrong for the weekly high and low as a second example, but the close direction and rank stay unchanged, there would be no ranks for the weekly high and low and the penalty for the wrong direction to regard.
Calculation:
weekly close: direction correct, 3rd rank: 2+2=4
weekly high: direction not correct, no rank: -1+0=-1
weekly low: direction not correct, no rank: -1+0=-1
total: 2 points.
If it's too complicated, you can leave it as it is now. This is made for discussion.