Aeneid book 12 (728-733)

I’ve been struggling to figure out what exactly is going on in these lines. I have looked at various translations but I’m still a bit unclear so some assistance would be greatly appreciated! Here’s the section + my translation/questions.

Emicat hic impune putans et corpore toto
alte sublatum consurgit Turnus in ensem (1)

et ferit; exclamant Troes trepidique Latini,
arrectaeque amborum acies. at perfidus ensis
frangitur in medioque ardentem deserit ictu,
ni fuga subsidio subeat. (2)

  1. This seems to translate as “Turnus rose with his whole body, having been lifted high onto his sword”, but that doesn’t make sense - is there an alternative way to interpret “in ensem” (and “alte”)? I can see all the separate components of this part, I just can’t find a way to make it coherent when it’s put together.

  2. “but the treacherous sword shattered in the middle of the blow and his passion would have failed him, if flight had not come to help”
    I assumed that “ni” is a conditional clause (or something like that) but since “deserit” is indicative I can’t quite figure out what’s going on - I thought it would have to be subjunctive? I also can’t figure out how “ictu” fits into the phrase - is it “in the middle of the blow”, or could it be “was broken in the middle by the blow”? I’m confused by all parts of this bit, to be honest - I’ve spent a lot of time trying to figure it out (and looked at various notes/translations) but I just can’t figure it out!

You need to respect the fact that Latin is an inflected language, so you have to pay proper attention to what goes with what.
What does sublatum go with? Not Turnus, which is nominative. What is it that’s “lifted on high”?

in medio … ictu “in mid-strike”

What’s the subject of deserit? and what do you think is its object? You can see that ardentem is accusative.

You’re right this is not a straightforward conditional sentence; indicative in the main clause, subjunctive in the if-clause. It’s strikingly elliptical: “The sword deserts him <and he’d be killed on the spot?> unless flight should come to his aid.” Once his sword is shattered, he can only flee—a sudden reversal, marked by the irregular syntax.

All the main verbs are present tense. Why not translate them as such?