Reciting aloud in the Sunnats and Nawaafils of the night

Q: I am currently becoming hafiz at the age of almost 40 (please make dua that I reach completion). I practice what I have learnt during the day by reciting it in namaz and in nawafils. After Esha I come home from the masjid and I recite quietly in the sunnats of Esha and loudly in witr namaz and in nawafils thereafter. I do not pray loud in nawafils during the day because I have been told that you can't recite aloud in the sunnats of (say for eg. Esha, maghrib) and that you can't pray loud in nawafil during the day (only at night), is this true?

I find it so much easier and more helpful if I read aloud, I find that reading aloud helps me retain what I have memorised much better. For the sake of my purpose (hifz-e-quran) would it be ok for me to recite aloud in sunnats of maghrib/Esha, etc and in Ishraaq and chast namaz in the privacy of my own home (without disturbing anyone)?

Sajdah-e-Sahw

Q: Is the sajdah sahw only waajib in those instances when it is allowed to pray? For example if one is praying Fajr and after the salaam the sun does rise, does he need to do sajdah sahw or his he absolved ? If not does he later need to repeat the Fajr (because he did not do sajdah sahw)?

If one praying Asr and after he makes salaam the redness of the horizon is visible, does he need to do sajdah sahw or is he absolved ? If not does he later need to repeat the Asr ?

Missing Salaah

Q: There is a lot of improvement in myself by the grace of Allah Azzawajal and by the dua of ulama-e-kiraam and  the Ahlullah. But the problem is that my Salaah gets missed when hard circumstances arises. I know that the commandment of Allah Azzawajal is most high. But I am helpless in this regard. When situations are favorable I offer Salaah in jamaaat. But while travelling or when there is no place 2 offer Salaah I can't fulfil SalaaH. I am extremely worried about that. Yesterday there was a student jamaat in our locality. I benefited a lot from that. But today only I went to a distant place for my vocational training. The musjid is very far from that place. I can't offered Salaah in open space. Kindly make dua for me and show me the path.