Advice on TAs / speedruns

I sometimes watch Turn Attack videos and got interested in doing them myself.
From what I’ve seen, the DPS itself doesn’t matter as much, since many players seem to rely on the supports for speedruns
…Unfortunately, I didn’t think about it at the time and gave 1K HP Fous to Skadi, which is a problem, since TA videos usually involve cycling out supports with either plugsuit or taunt CEs (and I wasn’t even lucky enough to get taunt CEs)

  1. With a 1K HP Skadi, is it impossible to do TAs at this point?

  2. No Waver, Tamamo or Chiron.

  3. my possible supports:
    Merlin (fully leveled)
    Osakabehime (fully leveled)
    Bunyan Lv. 50 from last year and Lv. 1 from this year
    Rider Ishtar Lv. 80 from last year and Lv. 1 from this year
    Archer Helena for her first skill (underleveled)
    CasGil (underleveled)
    Penth (underleveled)
    Cas Nero (underleveled)

  4. found this spreadsheet recently, but are there other very basic guides to doing TAs?

  5. Or is it too much trouble to even really bother with? I know TAs are heavily reliant on RNG and can take a lot of real-world time to pull off. Plus the materials to skill up characters who are deliberately kept at low levels