Those things which render the Salaah invalid

Surahs and du'aas in salaah with illustrations of the postures printed on a musalla for non-Muslims to perform salaah on

Q: Can these musallas be used for new Muslims so they can read the correct du'aas and surahs in salaah? 

It's basically a 1.5 metre piece of leather/strong plastic, and printed on it are; Surah Faatiha and two other surahs plus all the du'aas in salaah with an illustration of the posture they're to be recited in. 

The idea is for the new Muslim to pray their salaah on this mat, reading from it and following the illustrations as they pray their salaah. This mat goes directly on the ground and the person is standing on it.

Musallee looking inside the Quraan during Taraweeh and correcting the Imaam

Q: Please advise with regard to the following:

Is it permissible for a Musallee to look inside the Quraan during Taraweeh? If not, is there any social occasion in which it would be permissible?

If we are 3 people in our Taraaweeh Jamaat - the Imaam and one Musallee is a Hafiz, but their dhor is not so good and plan to improve it by performing Taraaweeh - will it be permissible for the Musallee to look into the Quraan during the Salah?

Meaning of Kalaamun naas when making dua in Salaah

Q: I am following Hanafi Fiqh.

1. In the current situation of Palestine, I have started reading Qunut e Nazila in Fajr prayer. I restrict myself with the Arabic dua from Quran and Hadith. However, I said one day, allahummansuril mujahideena fi filasteen (in Arabic). Would that be considered as Kalamun nas?

2. Secondly, could you please let me know about the guideline which will be easy for me to understand the Kalamun Nas discussed by the fuqaha. I have heard that if we are making dua in Arabic outside Quran and Hadith, it should not be in the classification of Kalamun Nas. However, this thing did not become clear so that's why I am refering to you.

Feeling laughter in one's chest when performing salaah

Q: The problem I face throughout the prayer is that I feel laughter in my chest. I think it comes from fear of breaking prayer due to laughter. There are times when I compulsively (quite intentionally) pronounce letters, especially "haa", mixed with laughter and sometimes, by forgetfulness.

Most of the time, voice cracks continously while reciting and very little part of my voice is audible (due to uncleared throat) and feelings of laughter seem to get mixed. Can you please let me know what is the type of laughter that breaks Namaz? I keep feeling every Namaz is invalid.