Gildas wrote:At what altitude would the rocket plane stop?
when he ran out of fuel .
If not for Apollo, I don't know the details of the thrust and flight plan, I'm just telling you that in theory you can escape the earth's pull without ever having reached 11,2 km / s, if you have a continual push. What matters is the speed reached at the end of the push, and the altitude where you are at the moment (there it must be greater than the release speed AT THIS LOCATION).
If the end of the thrust took place close enough to the Earth, the speed should not have been very far from 11,2 km / s since it varies in 1 / root (r)