LT
Was the unity of the deity of godhead ever broken?
Yes, when the Father forsook the Son.
If so, was God ever less than triune?
No, The Son did not cease to exist, nor was he annihilated as the jw's suggest. If we have a problem with this, we probably have a pagan ideal of death, not the Hebrew ideal of separation (death).
This comes back to the doctrine of the Tri-part man, as an explanation of how Christ could be foresaken and yet still remain in union.
I don't know about that. I don't know how we have relationships with the various parts of ourselves. We may have three parts, but, not three persons. (although after thinking about this, I catch myself talking to myself.)
It also helps us attempt to answer the question "can God die?".
Maybe the better question is "How can God die? not "if God can die".
D Dog