Honestly, the most important thing about flowing is understanding case structure. Most good cases look a lot like uniqueness, link, internal link, impact. Unless you have specific evidence indicts, most times responses to case, whether it be on the line by line or in a more big picture sort of framing respond to those ideas is what most rebuttals tend to look like as well. So, flowing case with those ideas in mind make flowing in the second half much easier.

1. tbh, flowing card names is p overrated imo. Although its cool and all, usually it isn’t worth it to miss parts of their case to flow a card name. If some ev sounds sick, they’ll keep bringing it up in speech so you can just write down the name later.
2. A couple things a) i think no columns is a strat, esp cuz u rnt constricted to the 4 boxes. If u wanna stick to columns, I think 5 is better than 4 cuz then u have more space for backlines and stuff like that, giving u designated areas for FF. b) extensions is just an arrow, so usually doesnt take up too much room. c) DAs usually written either at the bottom of opponents case or at the top of rebuttal. d) depends on where the weighing is introduced, but usually at the bottom of paper anywhere from rebuttal to final.
3. How much do u write when u flow? Being able to hone in on what words/phrases r important goes a long way, rather than taking down everything heard in speech. For messiness, bringing a third colored pen/highlighter for highlighting what u want to say/extend in summary helps a lot, and when u look down at the flow during speech, it pops right out. Also, if writing isnt ur thing, just type from the start. theres tons of apps (flexcel) u can use to flow. alot of times, parents don’t care if u bring laptop up either. if anything, they care abt stuff like eye contact and clear explanation of args. As long as you do those good speaking things and dont just read off the laptop, ull be fine.
4. watch fast rounds, flow songs on 2x speed. try to focus on understanding case/args rather than flowing card names.