If you've been playing this hard for 2 years and are still this preforming badly, then it's likely that it's more than just dyspraxia-related problems holding you back; players have gotten by with worse techskill (there's Broly, who
plays with his mouth, even).
At the advice of my higher-level friends, I've started practicing tech every day and playing about 30 hours a week for the last 6 months.
Personally I'd say my main problems are:
1.) Not recognizing/learning from my mistakes
What do you practice outside of techskill, and how much priority do you give that practice over practicing techskill? What are you currently doing to try to learn from your mistakes? How much active thought (not just raw time) are you putting into your practice in general?
It's really as simple as noticing what's going wrong and then thinking of how to fix it so it's not going wrong; the hard part is thinking of what to do instead, but then you can afford to experiment: "I keep getting shieldgrabbed when I do
this move on shield; so maybe I could spotdodge afterwards, or dash away, or space further away, or add a mixup with
this option, or I should just stop doing it entirely", and so on. Theorycraft anything you think may work, and try it out.
I suggest that your main goal for now, above and beyond anything else, is to make yourself aware while you're playing; that way you the foundation to improve. If you find that difficult, then use some sort of trick or prompt to help you; for example: when you're practicing alone, you could play 2 minute games against computers (instead of infinite time) and at the end of each game make sure that you haven't started autopiloting.
I know advanced tech (DI, shffl, wavedash, etc.) but I frequently input wrong/miss windows and don't know how to apply it in the right situations.
I never make it past the first round of a tournament and I still regularly lose to casuals.
Not knowing how to apply things in the right situations is a strategic problem, not a technical one. Losing to low-level players is often a symptom of not understanding your decisions (you develop habits that work against certain types of player, but you don't think about the reasons behind those habits enough to adjust to Marths that do nothing but walk forwards and f-smash, for example). It goes back to the previous point of evaluating where you're losing and what the solutions/your course of action should be. The key to adaption is awareness and active thought; you need to know what you have to change, and then you have to actually make yourself change it rather than just falling into habits.
I've asked several high level players what should I focus most on to improve and their answer was unanimously "everything"
That answer's true, though misleading. You do want to practice and be good at everything, and you can stand to improve in every area, but that doesn't mean that you need to practice everything at the same time (which is impossible, anyway). If you're maintaining an awareness of your gameplay, then you should be able to come up with things to practice easily enough. If you don't know what to practice, then just pick something on a whim at the beginning of the day and keep it in your mind whenever you're playing; for example: "today I'm going to explore the uses of wavedashing down out of a dash-dance", or "today I'm going to focus on my interactions with a shielding opponent". As long as you have some sort of goal, you're better off than you would be without one; even if the goal is as vague as "focus on punish game", that's something. Watching videos (which you should be actively studying) is helpful for finding things to practice, since you can just look for interesting things to copy from top players.
Wobbles has a blog which is extremely interesting and useful; there are too many relevant articles so I'll just link one of the first ones I saw that seemed to fit the topic:
http://www.compete-complete.com/2013/08/asking-right-questions.htm
Also, Wobbles has hand tremors and ADHD (which he doesn't medicate when he's at tournaments because it makes his hand tremors worse); though he doesn't discuss it much on his blog, it's a comparable issue to yours so it might still be useful to read about how he deals with it (you could also ask him personally on Twitter or Smashboards if you want).
