Cool video. It's not often that I see a younger person do paper flashcards like you did. I went through the same thing, and now only use electronic flashcards, and only for things I heard or wanted to say in real conversations. I completely agree with your philosophy of only learning the real language, and the approach you are taking to reduce your accent. I've done this in several languages. One thing you might try is to work with audio that has text, and in addition to doing your normal shadowing method, go back and try to read a line perfectly, then listen to the audio, and if you were off repeat after the audio. I found that when I worked through some material like that every day for a couple weeks, I would notice a big improvement. Your Portuguese is much better than mine, so take these things that I noticed with a grain of salt:

Regarding syllable/word ending r’s, if you use the American r, I think it is most common to say it bold and nasalize it (caipira). If your goal is accent reduction, because this isn’t a very common accent, you might want to switch to a single tap or gutteral r. I do not believe using a reduced American r, which I think you are considering, is a common accent. This is my source.

Não is a bit inconsistent; sometimes sounds like “now” in English. Same for some other words with ão.

Importar sounded like impordar; I think this was just a slip though.

Funcional; nal sounded like no in English, the l s/b pronounced like u

Tolice was stressed on the i and e, sb just i

Assim; words ending in im/em are a bit inconsistent; sometimes there is a strong nasal, sometimes it just sounds like you dropped the m

Deixo and similar words with ei sometimes sounded like e, sometimes like ie

Falando; a was not reduced. Generally, you reduced them, so this was probably just a slip.