I sort of recognise some of your experiences. I tried for an MSc many years ago, and sometimes I wouldn't get that final level of understanding until years after I'd passed the exam. Knowledge takes time and work to mature sometimes. You're just used to taking in a lot in a short time - which is a good ability - so you have no prior experience of this longer, slower process yet. Now might be a good time to think a bit about your learning style, look at what has worked in the past and what you aren't pleased with, and maybe try something new. I definitely think you can reach your goal, just by thinking about the problems and sharing your thoughts with us you are on your way there.
Word of caution though: It's a lot of work (and money) for a very limited career you are looking at. I do hope you have a plan B and C if you don't manage to land your dream job.
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