Everybody puts their own value on different experiences so can respect if OP wants to fly longer routing for D1 in a 763. I will just say you know 763 D1 is bad when a couple of years ago my 11 year old got on the plane and remarked this was maybe the worst business class he had ever flown and half the cabin agreed with him. LOL.

I appreciate everyone weighing in. My primary question was answered - if I want to do this, separate tickets will be ok.

As to whether I should divert to ATL to do this vs. a shorter routing in regular F.... Zorak hit the nail on the head for me. It is a long flight any way I go, and being able to lie down to nap or rest is an important factor for me to consider, even taking into account the age and design of the seat. The day will be gone. I will have either gotten up crazy early or will be arriving crazy late, so will be exhausted any way you look at it.

Thank you to everyone for answering my questions.