Getting this late but wanted to comment on your points:
For 1: This is really common. I still do this to myself plenty of times. Daigo talked about this concept in one of the recent FGC translated videos (can’t remember which one but it was one that someone posted here). Fundamentally we are still playing this game in really small pockets of time. Adding anything to make the process more complicated is going to slow the process down, and when you talking windows of frames any delay can be too much.
Kayin has a really good article about the mental stack and reaction speed: Reaction Speeds in Gaming – [K]ayinworks
An important point to bear in mind that comes up in that article is that even when you simplify the stack you’ll still get faster the more practice you get.
For 2: Yes. The more combos become just raw muscle memory, the easier everything around them becomes. I haven’t been playing Kolin that long but even now I have moments where I’m able to use her combos do other quick mental things, whereas I used to have to focus a bunch just to hit her basic juggle. Just keep at it!
For 3: I still fuck this up too. When in any doubt, block a bunch. If you watch pro player replays, one thing you’ll notice is how much they block on defense (varies by player of course). Getting squirrely on defense is the easiest way to die in this game and it is something people do surprisingly consistently (even when frame traps stop working so consistently you’ll notice people will still press stuff reflexively in a lot of situations, something I’m still working on).
I want to emphasize two things:
- It is impossible to understate how much the breaks and character switching resets your progress. Not being a dick, just being realistic. Changing characters is a big reset and when you change characters a bunch then step away from the game for a chunk, of course you’re going to have to reprogram a lot when you get back.
- Cut yourself some slack. One of the rough things about getting better at, well, anything is that there is often a lot to absorb. You are trying to onboard a shitload of information - basic movement, special moves, timing, spacing, normals, combos, VT stuff, all your opponent’s shit, the fucky throw game in SFV, etc., etc. - all at once. You have the right idea about compartmentalizing that info and making it easier to digest, but even when you do that don’t kick yourself too hard for not internalizing everything right away. Shit takes time.
To that point: you came on here posting about how you felt lost and hopeless, then after some reflection you came up with some solid ideas that will help you. The first post was basically a wake up DP in post form. 
Changing characters is bad for when you’re figuring stuff out; changing to an entire other game to try to learn is going to be worse. That allure of “maybe this game will be better for xyz” is one of the things that keeps you bouncing, which is fine for trying new shit out but clearly hasn’t helped you actually get better at the things you want to get better at.
And worth pointing out that you did come to an actionable, productive solution on your own. Just had to give yourself some time to come down and let things process. Sometimes that is just the case.
I have felt the way you do/did many times, especially after going like 0-50 against Akhos in a session. But I’ve found that 99/100 if I sleep on it I’ll come back to it the next day having some ideas of things I can work on. It doesn’t always translate into matches against him for a bunch of reasons but it sure as shit is translating into more and more of the other online matches I’m playing, so I get to see the progress.
Not to say don’t ask for help or anything - I’m always up for match reviews, for whatever that is worth, as are a bunch of people here - but don’t let yourself get so worked up if you feel lost or stuck for a bit. Happens to all of us, and time has shown that it is something that can and will be worked past.
Another dime length 
post.
