1- The best dua after every Wajib Namaz is Taqibaat of Namaz you may find in any app exam Dua.org or Shia Toolkit and Sahifa etc. Also no need to take everyone’s name you can hayat say I recite this Dua from my parents grand parents brothers and sisters and all those who has done favor upon me and all Momenin and Momenaat.
2- It has same Sawab there is no difference.
3- We can ask our dua and even we must ask our dua’s with the Wasila of Aimma Taherin (a.s). Yes you can pray Namaz for all Aimmah for more detail you can refer Mafateeh al Jinan at the end it has mentioned how to recite Namaz Hadiya e 14 Masoomin (a.s).
4-We have many Hadith regarding Tasbeeh of Bibi Fatima Zahra (a.s) we must recite Tasbeeh after every wajib namaz just after Tashahhud and Salam then you can do Last Sajda e Shukr at the end.