That's a limitation of language.

Feeling sometimes mean our emotional reaction sometimes mean a physical sensation.

Nah that makes sense for me, I think it's suggesting that because of Marty's crash, or rather a sequence of events following the crash, his future is so crap. He needed a spiritual awakening before the very next day in the present, in order to fully dodge bad things that could happen in the future ('85-2015).

When Doc and Marty decide the future is fixed, they do so by looking at a newspaper in 2015. They're clearly not looking at everything - Doc isn't trying to fix marty's life holistically.

If it was just a question of Marty being a bad dad out of dis-preperation, rather than out of trauma, yes it could be fixed by just setting foot in the future or hearing that his son had a problem. (Remember he also has trauma regarding his family's upbringing in 1985-V1, original present. And he probably decided Doc Brown would save him if things ever got really bad, but Doc never intervened - until now, when his son might go to prison)

Also what helped, though, would be seeing his son in person, and specifically seeing how he parents and how despondent his son is, and then figuring out what went wrong.

Ah, but you mean "Doc just needs to have one conversation with Marty to save the future." I... yeah that's true. What he needs to warn him about, though, is racing Worms/Spikes/whatever that guy's name is. And i guess it's not a plot hole that Doc does not realise this. He's a scientist who doesn't understand human connection so well (evidenced more in 3rd film). Maybe that is a big reason why the timeline only stabilises when Doc meets his wife 😀 🥰.