Regarding quant, you can score Q51 with a missed question or possibly even with two missed questions. At the same time, your total score is not exactly based on your section scores. Rather, both your section scores and your total score are based directly on the number and difficulty of the questions that you answered correctly. So, Q51 with one missed quant question and a certain verbal performance often results in a total score lower than the total score that results from Q51 with no missed questions and the same verbal performance. So, the goal is not just to score Q51 but to get as many quant questions as possible correct.
To do so, work question type by question type, strengthening weaker areas. Any kind of quant question that you don't feel comfortable with you need to master answering, so that you go from preferring not to see questions of that type to being excited to see questions of that type.
Regarding verbal, you have partially answered your own question, by making clear that you have to work on RC more, possibly by using LSAT RC resources.
Regarding SC, the fact that you have run out of practice questions is less of an issue that it may appear to be. You can get a LOT from carefully analyzing official SC questions to see what makes them work, even if you have seen them already. One exercise that you could use is going through SC answer choices to find two flaws in each incorrect choice. While, of course, this exercise doesn't work if a question has short answer choices, most SC questions have choices that are flawed in two or more ways.
You can also reanalyze CR questions in a similar way, seeking to see more clearly than you have in the past the key details and logic that make the incorrect choices incorrect and the correct answers correct. There is so much to see in the questions, and it's likely that, in your training, you have seen only a fraction of it.
Have you used these questions?
https://www.mba.com/exam-prep/gmat-offi ... -questionsIf not, you could get some practice by using them. Just make sure that you practice untimed, making a point of seeing as much as possible in each question before choosing an answer. Given all the prep you have been doing, if you practice untimed, I bet you can achieve hit rates close to 100 percent. Do the same with the LSAT RC passages, practicing untimed and shooting for hit rates close to 100 percent. You have to learn to get questions correct. Once you do so, you can seek to speed up.
You could also practice by using non-official questions. Yes, many are flawed, but some are good enough that you can use them to train to see what there is to see.
While I'm not sure how many more points you need in order to hit your score goal, it seems likely that, by putting yourself in a position to get a few more quant questions correct, by learning to see more in SC and CR questions, and by putting some time into RC, you should achieve your goal.