Writing the rules of Tajwid in the margins of the Mus-haf

Q: We are a group of students who want to study the rules of Tartil (slow recitation of the Qur'an) according to Warsh recitation style from the narration of Al-Azraq. The Mus-hafs (copies of the Qur'an) we have contain the rules of this recitation. However, during our study we need to write down some rules in the margins of the Mus-haf in order to remember them instantly while reciting the Qur'an in the manner it was revealed, as Allah (Exalted be He) says: And recite the Qur’ân (aloud) in a slow, (pleasant tone and) style. For example, Allah says: مَا لَكَ لاَ تَأْمَنَّا عَلَى يُوسُفَ [Why do you not trust us with Yûsuf (Joseph)]. We underline the word "تأمنا" [Ta'mannah - trust us] and we write beside it in the margin that this word contains the rule of Ishmam (pressing the lips together in a voiceless manner as if pronouncing Dammah) (Part No. 3; Page No. 53) and Al-Rawm (uttering only part of the letter sound at stoppage).1. Is it permissible to write in the margins of the Qur'an? It should be noted that we read in the endnote written by Shaykh Al-Hudhayfy in the Mus-haf distributed by King Fahd Complex that there is Ijma` (consensus) among the early Muslim generations that nothing should be written down in the Mus-haf except the Ayahs (Qur'anic verses).We have noticed in this Mus-haf that the number of the Ayahs is not written for the previous reason. Taking the impermissibility of this matter for granted, what is the suggested way whereby we can learn the rules of Tartil according to Warsh style?2. Is it permissible to write down briefly the causes of the revelation of some Ayahs and their Tafsir (explanation) in the margin of the Mus-haf or not?3. Is it permissible to write the number of some Ayahs for the sake of counting or clarifying the unfamiliar words in terms of the way they are written and uttered?For example, we place 3 above the word "أيه" [translated as O you] in the following Ayah: سَنَفْرُغُ لَكُمْ أَيُّهَ الثَّقَلاَنِ [We shall attend to you, O you two classes (jinn and men)!] to indicate that it is repeated three times in the Qur'an.