Method of Salaah

Skipping one short surah in the qiraat of salaah

Q: I recently found out when reading Salaah one should not skip one Surah between, e.g. during Magrib you should not read Surah Nasr and then Surah Ikhlaas. I know people skip two surahs, I’ve heard them read Surah Nasr and then Surah Falaq. So my question is, is it okay to skip if two or more surahs are skipped? 

My second question is if you are reading a long surah for example Surah Yaseen, is it okay to read the first 10 ayats in the first rakaat and then read from the 25th ayat to the 30ayat for the second rakaat? So basically skipping ayats and continuing? Is that allowed or is it Makrooh?

Reciting a surah after surah faatiha before going into ruku

Q: I was praying maghrib. After reciting Surah Faatiha in the first rakah I forgot to add another surah and was going for ruku. I opened my arms but just when I said "Alla-"(of Allah Akbar) I realised my mistake. I once again joined my arms and recited the second surah and did rest of the salaah normally. I did not do sajda sahw. Is my prayer valid? 

Also is sajda sahw valid for all mistakes in salaah or is it invalid if you missed fards of salah?

Keeping the head straight during qiyaam

Q: 

1. Would it be disliked if someone bowed their head till their chin touched or almost touched their upper chest, in the standing or sitting positions of the prayer (while keeping their eyes at the various sunnah positions during the prayer)? If so, for what reason would it be disliked, and when would it not be disliked? 

2. If they did this out of feeling comfortable, would it be disliked?

Acquiring concentration in one's duas and salaah

Q: Please advise how to soften my heart. I recently cannot cry. No matter how afraid I am of my sins and meeting Allah Ta'ala, I cannot cry when making dua. If it's my medication, do I stop it? What if I battle without my medication? At the same time, I'm worried about becoming hard hearted. 

I also cannot concentrate at all in my salaah. How do I become a better Muslim?