First of all, congrats on the guide! Im very interested on this because of high DPR while mantaining a good spell progression. This makes the already powerful sorclock into a beast by using hexblade's bonuses and divine soul's bigger spell selection, which is exactly what I was trying to come up with on my own. Sure the fighter multiclass dip could do even more damage, but you would stretch your spell progression even further (you are already 2/3 levels behind with warlock, add fighter and now you are 5 levels behind, which equates to a 3 spell level difference for the entire game). Adding fighter would also mean you lose a feat / asi, a metamagic choice and 2 more sorcery points. The way I see, this build shines not as the best theoretical possible DPR ever, but as a high DPR build with a great utility / versatility, and to me the 2 level dip into fighter just makes you better at something you are already good at, while becoming worse in every other aspect while significantly delaying your spell progression.
One thing I realized that wasn't mentioned, is how awesome elven accuracy gets with hexblade curse. You can alway re-roll your bad roll with advantage, so this means 3 chances of getting a critical hit, on a 19-20. This translates to a whooping 28.1% crit chance, so its very likely you are gonna get at least one critical hit per EB use (71% of getting at least one crit per EB, or 92% on a double quickened EB). I dont think you factored critical hit damage into your DPR math, but its cerainly not neglectable. Considering my DM uses a critical hit table for added effects, this makes the build much more powerful against bosses in my table.
Doing the math, the added damage from crits with elven accuracy and hexblade's curse on a EB would be 4 * 0.281 * 5.5, which is about 6 extra damage. So in the examples, first round would be 72, second round 86, and third round 172. If you don't cast hex on the second round, and instead double EB, you would deal 72 + 144 + 144 = 360 vs 330 with hex. On the 4th round, the comparison would be 504 vs 502, with hexblade still doing more damage than hex, but by a small margin. Only on the 5th round would casting hex do more, at 674 vs 648. So for "fast" fights that last at most 4 rounds, using only hexblade's curse for single target damage is the better choice.
This is pretty significant considering that hex requires concentration, and you usually need the concentration slot to give yourself advantage/elven accuracy anyway. This also means that it should be pretty rare to need to use both hexblade and hex together, and it also demonstrates how powerful hexblade's curse with EB actually is. I believe this fact should be added to your guide, as most fights you will either use hexblade's curse (big bad boss of the day) or hex (normal mobs), hardly ever both at the same time.
Now, if only my DM would allow drows/half-drows into the campaign, I would get that tasty extra farie fire and darkness

... But alas he does not, so Im stuck with half-elf

. I guess Im gonna go with the archfey patron for it, since its really an amazingly good spell