Translation of masoretic note for Psalm 24: 3 (מִֽי־יַעֲלֶה)

I've just finished working through Israel Yeivin's Introduction to the Tiberian Masorah and have had a jab at translating the note for מִֽי־יַעֲלֶה in Psalm 24: 3. It's not easy as the notes consist of inconsistent abbreviations and are mostly in Aramaic (which I can't read ... yet). In fact, at one point in time they were so incomprehensible that they lost their function as guarantors of the text and became decorative devices on the corners of the manuscript (Yeivin). G. Weil also notes that

As early as the 16th centruy Elias Levita wrote in the second rhymed introduction to his Massoreth Hamassoreth (Venice, 1538) that the language of the Masora was unintelligible, the very conciseness of its style making it as secret as the words of a sealed book.

To add to my workload, the wording of the masoretic note to my word differs in the Masorah parva and the Masorah magna. I'll post the two quotes in the original below along with my translation, culled from both sets of notes. My three questions are:

1. Is my translation OK?
2. What is the difference between the Mm and the Mp (I can't understand all of the Mm)?
3. Why was this information of signifance to the Masoretes? Did it really help them preserve the accuracy of the text, or were there other considerations at work?

Masora parva:

ג̇ ר״פ מי וג̇ מילין רביע ומי וכל פסוק̇ דאית בהון ח̇ מילין

Masorah Magna:

ג̇ דראשי פסוק̇ מִי ותלת מילין ורביעית וּמִי ומינין כל פסוק̇ ח̇ ח̇ מילין

Here's my translation, based primarily on the Masorah parva:

(One of) 3 (occurrences), (in which there is) a “who” at the beginning of the verse and (then) three words, the fourth (of which) is “and who.” And the whole sentence contains within it 8 words.

For those who are interested, the references (סימנהון) are Ps. 24: 3; Job 34: 13; and Job 36: 23.