Father, Son, and Holy Spirit has always been one and never separate. Distinct but definitely not separate. In the same way, Husbands and wives are distinct from each other in that the husband is the head of the house and the wife is not, but they are one. The Bible never says that the husband and wife is separate, but there is a distinction. A distinction is not a separation. I hope that helps in explaining it more.
Ok. Father Son and Holy spirit are all God yes. The comparison to husband and wife is still a little sketchy though. A husband and wife perform different and independent things while being in unison. They are in eachothers presence in essence but not always physically.
I suppose I get you, but I still can't apply that the Father died on the cross this seems specifically related to Jesus. This doesn't line up with what actually happened nor with any analogies I can find in the bible. For instance Abraham offering Isaac on the alter, but God instead providing the sacrifice etc.
We can say God the Son died, but we can't say the Father or the Holy Spirit died. If we die that doesn't mean the Holy Spirit , Jesus , or even the Father in us dies.