Seeking Clarity

I Seek clarity for peace of mind. Please forgive any repetitive questions: 1. During prayer, if I suspect a mistake in Al-Fatiha but am unsure due to my limited knowledge, should I repeat it or continue and complete my prayer without Sujud As-Sahw? 2. If I pause after "Siraatal-lazeena an'amta 'alaihim" in Al-Fatiha and continue(this can happen multiple times in one prayer(e.g., Dhuhr Fard(4 rak'ahs))) and complete my prayer, is my prayer valid(is stopping here permissible?), or do I need to perform Sujud As-Sahw? 3. In congregational prayer, if a front-row space remains unfilled, does my prayer in a back row remain valid, or do I need to perform Sujud As-Sahw? 4. For Wudu, is thoroughly swishing water in my mouth and inhaling deeply into my nose required, or is putting water in/out and a light inhalation sufficient? 5. During Wudu, if I am unsure whether I completely wiped the nape of my neck, must I repeat the wiping for certainty? 6. Is it best to ignore doubts in worship and consider my acts valid? I often repeat prayers due to concerns about: 6.1. Recitation accuracy(any verbal parts). 6.2. Prematurely moving before completing recitation(e.g., prostrating during Tahmid). 6.3. Omitting an obligatory part(e.g., Sujud Tasbih). 6.4. Tongue movement, noises, speaking, or laughing. 6.5. Insufficient pauses between elements of recitation(e.g., between tasleems at the end of prayer). Thank you for reading. These doubts affect my peace of mind, and I seek guidance.