Time to address rebuilt engine oil consumption

If you have poor/sticking oil rings, then the compression tests will typically turn out decent due to the sealing of the compression rings by the oil, even if the compression rings are not in good shape. So in this case, I would not take the compression tests as the data on which I would make a final decision, especially since all cylinders build evenly and quickly. But it would indicate that the head gaskets are sealing so a leak there seems unlikely.

A bad or no PCV system can cause crankcase pressure that can cause oil burning too. The OP has not mentioned the PCV system installed. We need to know that.

From the 1st post, the burning of oil out the tailpipes when at or near WOT cab a pretty conclusive sign of poor ring sealing, ASSUMING that the intake is sealed well AND the PCV system is working. The rate of oil burning also points to the same thing.

My plan would be to:
1) Examine and reseal the intake and test to be sure that is not the issue.
2) Look at the PCV system too.
3) Get ready for a re-ring or rebore/re-ring job. I would look hard at bore taper and roundness if it was not done before, and follow proper break-in procedures. When you get to that point, it might be well to discuss what others do.

I have rarely done leakdown tests (except on a small aircraft engine) so have to follow the judgement of others on that.