I agree completely: in many ways the 2 p&f combinations, both from Book 1, are among the MOST DIFFICULT of the lot. Angela Hewitt has said--for the reasons you've given--that the A Major fugue is THE most difficult, both to memorize and, as well, to play coherently. My own view is that the A Major and A minor from Book 1--completely different challenges--are equally horrendously difficult.
The word "difficult" merits some comment: often it's used in piano performance to refer to "mechanical" difficulty: for example, the octave-playing in the last movement of Brahm's PC 2, which he marks "pp" but which seems impossible to play at pace that way. Arguably, the word "difficult" in piano performance refers with as much force to the CONCEPTUAL difficulties raised by a number of Bach fugues, perhaps in fact almost ALL of Bach's fugues. Proof of this pudding is the fact that so many recordings and live performances of the Well-tempered fail (at least to my ears) to satisfy; whereas as there are (for example) many performances to be heard of Brahms, Beethoven, Mozart piano music that, although not perfect, are still enjoyable.
Nope: something about BACH--and his keyboard music in particular--that makes it VERY, VERY difficult. Not "technically," in the mechanical sense of that thorny word, but "conceptually".
Having said that, you've picked two VERY difficult fugues (and their accompanying preludes) and done an excellent job. Frankly, I don't care much whether or not the sheet music is used or whether these are "memorized." I heard Hewitt playing the entire set live a number of years ago in TO, and mistakes were made; some of the mistakes were very, very serious. I'm happy to see the music in front of the pianist for this rep! Less scary for the listener.