This was a great scenario for discussion, thanks for finding it! 
The consensus we came to was the following:
In the scenario where you tie with your opponent, and you’d both take a casualty. Supposing your opponent assigns 1 casualty to a dude to cover that 1 casualty, they would be discarded. Which at that moment Hellstrome’s React comes into trigger. Supposing you boot your gadget weapon, to give one of your dudes with a GW a control point, and then that opposing dude is then aced instead of being discarded.
The key thing here is that while they were aced, and while they were a casualty, they were not “aced as a casualty”. The acing came from a separate result (Hellstrome) and not the ‘I will ace this dude to cover two casualties’. Additionally, this is very similar to a recent ruling regarding Justine In Exile and Harrowed.
Justice in Exile, similar to Hellstrome, does a special acing on a dude given a criterion (the dude was wanted and left play at the same location as a Deputy, during high noon). However, this acing happens after the dude leaves play, and thus when used on a Harrowed dude, the Harrowed dude goes to Boot Hill (as opposed to the Discard Pile, which they’d normally go to, if they were aced from play).
Similarly here, the acing happens after the dude was discarded. So they weren’t aced as a casualty.
Thus, they wouldn’t trigger a CP gain from A Fight They’ll Never Forget.
Given the following scenario that you bring up, you would only gain 1 CP (from Hellstrome).