Very understandable that you did not react in time - the situation is very baffling
and I am always annoyed with myself that I do not react more quickly, elegantly,
and more decidedly to events like this one.

I found myself on AU domestic flights where the pax being mex demanded that
I would not lower my seatback as he had very long legs, only to find myself
behind a pax who would not put up his seatback at any time (including taxi,
take off, and landing) as he felt back pain on the return leg. And I did not find
the strength to buzz an FA to correct the situation.

Your situation must have been very unpleasant, and I assume that there was
no chance that you could have switched seats with the overweight pax, so
that you would have been at least squeezed next to your wife.

What I wonder how did the pax in the middle survive the flight? Four hours
sitting on two armrests that sounds like torture ...