I understood your question exactly but am sorry your understanding what “God exists outside if space and time” means is lacking.
And since the Father, Son and Holy Spirit are ONE - the Trinity does not exist separately - ever.
For the Greater Glory of God
So when it says He ascended and was "received into heaven" it doesn't really mean that?
Mark 16:19 So then after the Lord had spoken unto them, he was received up into heaven, and sat on the right hand of God.
And when He sat at the right hand of God He had really been there the whole time?
Is Christ still ascending? Is He still dying on that cross? You did say "His sacrifice is happening NOW because to Him ther is no past, no future - only His eternal NOW". So which is it. Only some things are happening perpetually or just some things?
You might want to check that.