Iliad 1.158 and 1.212

[vir litterarum]

ἀλλὰ σοὶ ὦ μέγ᾽ ἀναιδὲς ἅμ᾽ ἑσπόμεθ᾽ ὄφ?α σὺ χαί?ῃς,
τιμὴν ἀ?ν?μενοι Μενελάῳ σοί τε κυνῶπα
π?ὸς Τ?ώων
1.158-160

Is "espometha" a gnomic aorist? if not, why is "chairhs" not in the optative mood?

ἀλλ᾽ ἄγε λῆγ᾽ ἔ?ιδος, μηδὲ ξίφος ἕλκεο χει?ί:
ἀλλ᾽ ἤτοι ἔπεσιν μὲν ὀνείδισον ὡς ἔσεταί πε?:
ὧδε γὰ? ?ξε?έω, τὸ δὲ καὶ τετελεσμένον ἔσται:
1.210-212

Is τετελεσμένον ἔσται future perfect periphrastic?

[modus.irrealis]

Is "espometha" a gnomic aorist? if not, why is "chairhs" not in the optative mood?

It seems natural to me to read it as a normal aorist and I was going to say that the subjunctive is there just because the "sequence of moods" isn't always observed. But I double-checked and saw that Monro says that subjunctive is not used to express a past purpose -- either the aorist is gnomic or the purpose is still felt to belong to the future. So the meaning here would be something closer to "we have followed ... so that you ..."

Is τετελεσμένον ἔσται future perfect periphrastic?

That seems to be the case to me. I don't see what other possibilities there are -- well, maybe participle + εἰμί but I'm not sure that would really be any different.

[vir litterarum]

so the aorist here is actually translated as a perfected because it expresses a present condition resulting from a past action (Smyth 1940)?

[modus.irrealis]

I'm not sure if in the Greek the aorist is actually being used as a perfect or if it's just English grammar that forces you to use the perfect in the English equivalent. I think it's the latter because I know in other languages which have an aorist/perfect distinction, you don't use the present perfect even if the purpose is still thought of as being future. So I'd say that it doesn't express a present condition and just acts like a usual aorist.

[perispomenon]