I, too, have been a student of the martial arts since 1976. I've studies many different styles in the past 40+ years including two hard Japanese Karate disciplines, Judo, TaeKwonDo, BJJ, Hakko-Ryu Jujitsu, Aiki-Jutsu and FMA. Boxers scare the crap out of me, especially experienced ones.
In the real world (i.e., not in the ring) a fight with a boxer has to be fast and dirty. They know how to take a punch, how to move and how to strategically strike. The oft-mumbled advice of "kick a puncher/punch a kicker" doesn't necessarily apply to boxers, unless you're going to kick below the belt.
And that is about the only way to quickly disable a boxer. . . groin shot, knee shot or solid kick to the outside of the thigh to demobilize them (the latter is the least destructive, but you do really have to know how and where to kick to be effective).
Even good BJJ fighters don't worry me as much as boxers. With my BJJ, Judo and JuJitsu skills, I can generally drag out a ground fight until the guy gasses out. The trick is to fight to a stalemate, make them work it. This usually works on younger, less experienced guys.
But a good boxer? Take away his mobility, preferably grounding him and strike him in places he's not used to getting hit.
And PRAY HARD that he doesn't get into your OODA Loop and make you react to his set-ups.
Another way is to try to attack his hands, but that often does not work as well as it does on others (by "attacking his hands," I mean strike at the two weaker fingers of his fist. This is taught as a sub-style in some Chinese arts. I picked it up from a practitioner in Germany many years ago and it has gotten me out of many protracted fights as a young man. You do need the eye and reactions of experience to recognize the precursors to strikes and catch the fist/hand as it extends, but breaking the ring and pinky fingers often snuffs the blazing flame of a drunken aggressor's "bright idea").
Not fun facing even a mediocre, well-trained boxer. Not fun at all.
The Professor