I am a repeat test taker too. I definitely agree with what you said. I took mine at August all the way to 130 questions. I was absolutely helpless during the exam because alot of the things were stuff I didn't completely understand. I only used UWorld to study but I think that simply wasn't enough for me. I ended up using Hurst and started from the beginning. I watched all their videos under core content, from cardiac to GI. I also would suggest learning test taking strategies. Their are so many out there and it was super helpful, that when I took the NCLEX the next time even if the topic was unfamiliar I could tell which ones just sounded right.
What I would suggest is going back to the way you know you studied in school that was efficient. For me it was rewriting and saying outloud everything I learned.
I wish the best of luck to you! I know you'll pass the next one!