Times like this is when I wish we still had Gyarados around. I'd just say "lol1111 use Gyarados bam ggez"
But really, EV and IVs are still not all that important nowadays. They were never important, tbh, but now, with some of the gym leaders nerfed? yeah, it doesn't really matter.
What really matters, is that you pay attention to the FIELD EFFECTS. Most of the time, there's always a way to turn the field effect in your favor. That's easier said than done, but it's still possible.
Chubbs already answered your others questions, so yeah. But really, Reborn is easier now than before, imo.
You should totally give the game a try again. Heck, even restarting might be a good idea, since you're not really all that far.