Sajda-e-Sahw

Reciting softly in fajr when one is performing Salaah individually

Q: I was praying my Fardh Fajr Salaah and I did not recite loud like I do in the loud prayers and more like how I recite in the quiet prayers and so I continued reciting how I was so as to keep consistency in the salaah. At the sitting position in the second rak'ah, I said up to "Ashhadu anna Muhammadan 'Abduhu Wa Rasooluh." and said "Assalaamu 'alaykum wa Rahmatullaah" to my right then faced forward and prostrated (I intended to do the two prostrations of forgetfulness for not reciting out loud like I usually do for Fajr Fardh). During this, I got up from prostrating and raised my index finger and was about to start reciting "Attahiyyatu lillaahi Was-Salaatu Wat-Tayyibaatu." But then, I was confused whether I prostrated once or twice, and I leaned to the decision that I had only prostrated once so far and so I said "Rabbighfirlee" three times and prostrated for what I assume to be my second prostration. I sat back up and said the Tashahhud, Durood and Du'a, then I said both Tasleem. Now I wonder is my salaah valid?

Repeating Surah Faatiha in Salaah

Q: I was praying salaah on my own and I was reciting Al-Faatihah and then I felt confident that I missed an ayah, but wasn't sure which one and I knew for sure I had recited up to "Ar-Rahmaa-nir-Raheem." So I hadn't yet completed Al-Faatihah and I went back and recited from "Maaliki Yawmid-deen" until the end. I also in the same salaah was unsure whether I made two or one prostrations and did one more to make sure and after salaah I made two prostrations of forgetfulness for these mistakes and for any other mistakes I made. Then in the two prostrations of forgetfulness, I doubted whether I said the second part of the Durood  "Allaahumma baarik 'alaa Muhammad..' (peace be upon him) and so on. But I thought it was a doubt and ignored it, but don't recall doing it now. Is this OK? Anything I have to do?

Doubts with regards to sitting up straight between the two sajdahs

Q: It is stated in some hanafi fiqh books that it is wajib to sit up straight between the two sajdas (Jalsa). I keep having this problem where I keep thinking that I haven't sat up exactly straight between the two sajdahs and think I've missed a wajib and would perform sajda sahw. Is it necessary that I have to sit up exactly straight between the two sajdas or is there some leniency that for this sitting up straight is approximate and not exact?