Yes all of that makes sense of course. If other roots and branches were discovered this would be incorporated into the theory and evolution as a story adapts. But that is rather my point.
You started by saying evolution is a fact. I said it's more complicated than evolution being a fact. You said okay but even if the details of evolution change, common ancestry of all life is a fact. But when I point out this fact may also be subject to revision you agree but insist this doesn't alter the fact of evolution.
Which is problematic because it produces assertions that are in tension with one another:
1. The details of evolution may change but common ancestry of all life is a fact.
2. We may discover that not all life has a common ancestor but this doesn't alter the fact of evolution.
So what is an unalterable fact? Apparently neither evolution nor common ancestry of all life, because as soon as you focus on one the other becomes unstable.