Sort of yes, but I need to ladder more. I sometimes click on the "obvious" move/switch without reconsidering better options, but I've gotten better at stopping that habit. I'm pretty satisfied with my battling skills aside from needing to practice and learn SM OU.
No.
I really haven't battled competitively since BW. I remember being really into UU and Ubers in that time period, and I had so much fun with it! Afterwards though, I felt like I was a terrible battler simply because EVs are a lot more complicated than simply throwing 252/252/4 on most things and that's where I kinda just gave up, really. I couldn't figure out what EVs were appropriate for wihch Pokemon for which movesets and sometimes I felt like I was completely on my own on figuring out the optimal EV spreads which made me feel stupid.
Copy Smogon's EVs and add or remove Spe EVs
according to what you want to outrun. I remember custom min/maxing my EVs, using the damage calc to determine EVs to avoid KOes from specific Pokemon, etc. Good times. I don't bother doing that much anymore lol.