οὐδ᾽ ἂν σέ, ὦ Κῦρε, περὶ ἐμοῦ οὕτως ἀπρονοήτως βουλεῦσαι,
this inf stands for aor ind with an expressing unreality, doesn’t it?
εἰ δὲ Κῦρος οὕτω γιγνώσκοι, οὐκ ἂν ὑμᾶς, ὦ Μῆδοι, ἐθελῆσαι οὕτως ἔρημον ἐμὲ καταλιπεῖν.
The first opt stands for imperf in oratio recta, and again, inf with an stands for unreal ao.
Yes, that’s right, though γιγνώσκοι is ambiguous between representing pres or imperf ind.
in 2623 Smythe says that all past tenses with an remain unchanged. So maybe an should go with ᾤμην?
It’s true that past indicatives in subordinate clauses usually do not become oblique optatives in indirect discourse so as to avoid ambiguity. There are exceptions, though, and I think mainly in Xenophon. Rereading, however, I would actually take it as representing potential optatives not past indicatives. That is, direct speech would be:
εἰ δὲ Κῦρος οὕτω γιγνώσκοι, οὐκ ἂν οἱ Μῆδοι ἐθελήσειαν…καταλιπεῖν.