That is not a fact. He said that there had never been a human/Timelord
Metacrisis before, not hybrid.
Yeah, but combine that with the five thousand times he's said he's a Time Lord, no qualifiers -- and especially "The Runaway Bride," where he explicitly describes himself as being non-Human -- and the fact that "Journey's End" establishes that a Human/Time Lord combo can't survive, and I think you have a fairly obvious authorial intent: The Doctor is fully Time Lord and that part of the TV movie has been retconned.
There's a difference between a child born to human/Gallifreyan parents and what happened to Donna.
The child would have a combination of traits of both parents as happens to any child now. But in Donna's case, she had the in rush of the Doctor's entire knowledge (not sure she picked up any physilogical material though) and her brain just couldn't cope which is why the Doctor wiped her mind of the time she spent with him. It's akin to mating a huge V8 to a transmission made for a 4cyl engine - it 's going to work for a little while then come apart in a big way.
Now the quesiton is asked above what about the Doctor who's living on the parallel Earth with Rose?
In that case the human material has gone into a Timelord at a genetic level and as we're the inferior species in this instance it doesn't cause the stress.