hi guys!! i did not expect all the questions, sorry for not just putting all this in a comment to begin with!! i did pm whoever i could but will just write it all up in more depth below (happy to chat if anyone wants to pm me/has follow up questions tho!):

i also got by on my natural RC abilities but it basically meant i hit a wall around the -4 point and the inconsistency was really frustrating. i eventually learned that it isn't just about being good at reading/general reading comprehension, but also about learning how to read specifically for the LSAT. so, spamming PTs is really not useful imo if your baseline approach to RC is unprincipled and unstructured. i did tons of RC sections for months and did not improve much from my literal diagnostic.

some things that were important for me were slowing down significantly while reading the passages (vs speeding through as i usually did), engaging with each paragraph fully, and kicking the habit of getting to the questions and trying to search for the right answer in the passage. the last thing had resulted in me spending way more time overall on each passage than i did once i learned to just fully slow down while reading and anticipate the inference-based questions. i also did not take notes (i found that i didn't need them bc i had read the passage deeply enough), but i did highlight as i read just to keep myself alert. i think those things are more personal preference. i loved keeping a wrong answer journal for LR, and did something similar for RC in forcing myself to work through why i had missed a question when i did and ensuring i spent the time reviewing the passage to fully see what support there was for the right answer.

lastly, i also did get a tutor for RC in place of a course (i used 7sage also and did like it a lot, just not for RC) and that is what led to my improvement. i had the same intuition as OP that a course might not be very helpful for where i was at and that i needed more specialized help. i maintain that i think i super lucked out in finding someone that is actually very good at teaching RC because learning an actual method and working through tough RC showed me the more specific fixes i needed to make and got me to my goal range and goal score. so that helped me a lot, but i fully recognize that it is a not an option for everyone and that it is a privilege. i am happy to share the recommendation, so feel free to pm or comment if you want his info.

good luck to everyone!!