I'll answer this part of your post and leave the other questions to Arabic language specialists: أيخفى هو تساؤل يعني: ألا يظهر ذلك بوضوح؟ Meaning: Isn't that clear or obvious?

أيخفى = Is it hidden عنك = from you ذلك that (thing) the أ is inquisitive part = Is it فأجابني: أيخفى عنك ذلك؟ فكان كمن يقول: إنّ الأمر على غاية من الوضوح = then answered me: Is that hidden from you? it was as if whom says: that the issue is of high clarity Is ذلك the subject of يخفى ? >>>> Yes Is يخفى a 3rd person male passive non-past form? >>>> Yes, it is continuous about a third masculine object there's a sense of surprise about the fact the third object continues to be unknown.

1) (أ) is a letter of interrogation ( همزة استفهام ) as(هل ). 2) (يخفى)verb conjugated in the present , and Its subject is unknown . ( فعل مبني للمجهول ) Verb:أَخفَى=يُخفي ، إخفاءً or خفى=يَخفِي ، خَفْيًا 3)You should know first that in Arabic there are three letters ( و- ا- ي ) named ( حروف العلة ) .that exist in some verbs composed of three letters 1) If we have a verb ( فعل صحيح ) of 3 letters without ( و- ا - ي ) : Exempl:كتَبَ - At present , with a known subject =الولد يَكتُب -At present : subject is ( مجهول ) ( unknown ) =يُكتَب 2)The verb ( قال ) is named ( فعل أجوف ) because the letter in the center, is part of ( و ا - ي - ) If we have a verb with 3 letters, like ( قال ) the second letter is ( ا ),it changes into ( و ) at the present = الولد يقول in the unknown subject, you change ( و ) of ( يقول ) by :(ا) => يُقال 3 )رمى= فعل ناقص The verb ( رمى ) conjugated in present => ( يرمي ) , has a letter ( ي ) at the end . NB:(ي) is also part of 3 letters (و ا-ي-) To the unknown, we replace ( ي ) by ( ى ). =>=>( يُرمى ) 4 ) past: verb صحيح) =فتح) it changed in :فُتِح verb أجوف ) =قال) it changed in :قِيل verb ناقص )=أتى ) it changed in :أُتيَ