Ten commandments for judges

Question

The Ba'al HaTurim to Devarim 1:13 notes that the word ואשמם, "And I will place [the judges as your head]," is written without the י after the ש. (This is up to debate amongst the commentaries, and not for this discussion.) He writes that the lack of the י, whose value is 10, alludes to 10 commandments given over to judges. Although he does not list them, the Artscroll Ba'al HaTurim (Devarim, pg. 1813, note 41) quotes R' Chaim Kanievsky in his notes on Peirush HaRokeiach, who in turn quotes p. 140 of Otzar HaMidrashim, who in turn quotes Midrash Hashkeim.¹ That Midrash claims there are ten positive mitzvos and ten negative mitzvos given to the judges:

1. Don't show favoritism in judgement (Devarim 1:17)
2. Don't tremble before any man (Ibid.)
3. Don't pervert justice (Vayikra 19:15)
4. Don't favor the impoverished (Ibid.)
5. Don't honor the great (Ibid.)
6. Don't pervert the judgement of the destitute (Shemos 23:6)
7. Don't pervert the judgement of a convert or orphan (Devarim 24:17)
8. Don't pervert judgement (Devarim 16:19)
9. Don't show favoritism (Ibid.)
10. Don't take bribes (Ibid.)

The Midrash concludes by saying that just as there are 10 commandments to judges, so, too, there are 10 Commandments Statements, which shows that Hashem values the judges as He does the Torah itself.

Why does this Midrash list these particular mitzvos? The Rambam, at the beginning of Hilchos Sanhedrin (Sefer Shoftim), lists 30 mitzvos related to the judges. Once you narrow the list to those directed at the judges themselves, you get the following list:

1. To follow the majority
2. Not to convict until you have a majority of at least two
3. Once a judge votes to acquit, he may not change his vote to convict
4. To kill certain individuals by stoning
5. To kill certain individuals by burning
6. To kill certain individuals by beheading
7. To kill certain individuals by choking
8. To hang bodies that were killed in court
9. To bury those killed in court on the day they were killed
10. Not to leave those who were hung² for extended periods of time
11. Not to let a witch live
12. To give lashes to the wicked
13. Not to give too many lashes
14. Not to punish one who was forced
15. Not to judge on assumptions
16. Not to take pity on a murderer or damager
17. Not to favor the poor
18. Not to honor the great
19. Not to tilt justice against known sinners
20. Not to pervert justice
21. Not to tilt the justice of an orphan or widow
22. To judge righteously
23. Not to be afraid of the litigants
24. Not to accept bribes

So if there are 24 mitzvos directed at the judges, why does the Midrash list these ten in particular? Further, the Midrash starts off by saying that there are ten positive and ten negative mitzvos. If you want to say that over the years we lost some of the text and we lost the part that lists the ten positive mitzvos, fine. But the Rambam only lists nine positive mitzvos!

To sum up: How can the Midrash say that there are only ten negative mitzvos directed at judges, when there are much more? And how can the Midrash say that there are ten positive mitzvos directed at judges, when there are less?

(If someone can conjure up another Rishon's list of mitzvos that provides exactly 20 mitzvos, ten positive and ten negative, directed at judges, that would be an acceptable answer. We don't need to pasken a Midrash as Halacha, so there's no issue that the Rambam doesn't go like the Midrash; the question is which list the Midrash is using.)

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¹If somebody can find that original source, that would be great, but not necessarily necessary to properly answer this question.

²Hanged is only used when one was killed in that fashion.