That was exactly how it went down. Apollo was looking for revenge on Kal, Superman trounced him pretty severely.. using the Sun against Superman was a bad bad idea. Di and Kal were having a rough time with Zod and Faeora (always spell her name wrong) so Diana had mystical armor made that gave them an advantage. It looked like they were going to win but then Apollo turned around and super charged Zod and Fae with as much energy as Kal had gotten to defeat Apollo.
After the severe beating they were tossed into the nuclear well of doom. Kal wrapped Di in his cape and took the majority of the blast. I thought it was pretty wild, he depleated the very last of his reserves to survive and protect Diana an was reduced to what looked like a 6 month old corpse. But once he got some sunlight he was able to help fight off the last of their leftover foes and get Diana to safety an THEN himself.
They've been playing up Kal's lack of real combat training in the book so far, so despite his physical superiority he has a lot to learn from the Amazon, an that lack of training is why he just can't beat out Zod who's as capable an concomitant as any warrior AND nearly on par with Kal for pure power.
they need to remember in the DC that Superman powers are derived from accessing the Sun as a Solar energy source, but also due to Gravity/mass/density, as there is really no legit reason why he should ever become fully human like, as even depleted energy reserves wise, would have that gravity/density thing going!