Complex verb tense consistency variations

Ok so I’ve always faced a certain level of confusion regarding the conjugaison of the word “would“ when it comes down to some of its specific uses under various tense conditions.

For instance, the other day I had someone (a native speaker) throw the following sentence at me:

“I would take a shot if he fell asleep during the debate“

Please just don’t ask me what this sentence is referring to ?

So basically my question is why did he match “would” with the past simple tense of fall (fell) if the action he was describing was referring to something that was about to take place in the future? Why not simply use the 3rd person singular present tense (falls)?

I obviously had no problem understanding what he meant, but I struggled to grasp the reason behind his choice of verbs as the actions he was referring to were occurring at different moments in time and hence matching the tense made zero sense to me.

Would really appreciate if someone could clarify this for me. Cheers