Whenever we are at our physical limits, things get ragged. In the case of young trumpeters, we get range by force. The mouthpiece is mashed into the lips and then we try to force air to blow open those mashed lips. The results are what you describe. With more experience, we keep using force, but get more air pressure so we can hit a couple of high notes more. In our third state, we learn to use more brain than brawn. We have a couple of thousand lipslurs under our belt and if our teacher was any good, some decent breathing habits were developed.
For building range: Body use, breathing THEN chopbuilders like lipslurs!