apparently you are pretty makpid
lol did that on purpose.
Wow vayikra isn't one of the easiest parshas to start with so kol hakavod! Monday and Thursday is a great place to start as it's very short and like you said someone is almost always needed. You can spend some time on shabbos afternoon to prepare it and then go over our once before Monday and again before Thursday.
Regarding שוא נא ושוא נח my first few years of laining I wasn't careful but then I learnt an easy simon to remember them and i it became a breeze.
Yeah, I realized that as I was going through it. Unfortunately, I wasn't able to lain it last year so now I haven't looked at it in 2 years. That's a good idea for Mon-Thurs, but it's annoying because my Shul usually has someone for Mon/Thurs. I find the need for a Ba'al Koreh more when you're in a random place one morning. And at that point, I wouldn't have prepared it in advance.
I was always careful with pronouncing words clearly, but I didn't get too grammatical until my Hebrew class in college where my phenomenal teacher taught us everything about Shevas, Dageshim (still don't do that 100% properly), etc. I've gotten much more particular, but of course, would never correct a Ba'al Koreh who doesn't pronounce a Dagesh Chazak. In my community, many Ba'alei Kriah read "Ches" and "Ayin" in a gutteral way like certain types of Sefardim. I don't think I would ever end up laining like that, though.
The most interesting thing my teacher taught us was how he believes a Daled without a Dagesh should be pronounced - "Daleth". His support was quite intriguing. Everyone knows that Rashi says by Shema that the Daled of Echad should be stretched out. Yet, there's no way to really stretch it without ending up saying "Echaaaaad" (which isn't stretching the actual Daled, but rather the Patach of the Ches) or "Echadah" (which is really like adding an extra letter after the Daled." However, if you pronounce the Daled as "Daleth," then you can say "Echathhhhh" as that is a sound that can be stretched. Perhaps that's how Rashi pronounced his Daleds and that's what he meant. Thought it was really interesting.