OK I think I've finally figured out why my tabletop split apart. I
recently ripped it into individual boards again per your suggestions.
I then re-jointed all the edges. This time I noticed that if one end
was held flush against the mating board, there was a tapered gap
increasing in size towards the other end. I soon determined that this
was due to the relationship between my jointer blade and the outfeed
table. I made an adjustment to this. In the end, I adjusted the gibs
for both the in and outfeed tables to the point now where, using a VERY
flat, thick and wide, 4ft starrett ruler, I have the in and outfeed
tables adjusted within microns of each other and the relationship to
the blade is practically perfect (I spent 5 or 6hrs doing it--I hate
giving up!). Now when I joint the two mating surfaces, I get a
1/64inch gap in the middle but the ends are flush. I should say again
that my boards are 5/4 hard maple, 5.5inches wide and about 57inches
long.

Now my question to you JOINTER EXPERTS: Is this gap simply inevitable,
given that my combined in and outfeed table length is about 47inches
and my stock is about 10inches longer than that or is there something
else I'm overlooking?

I have the Yorkcraft 6inch wide jointer which is the same model as the
Delta.
Stan