You are supposed to run sudoedit.
This command creates a temporary copy, opens it in you editor of choice and overwrites the protected file when the temp file changes.
That way the editor doesn’t run as root.
You can see the difference if you run shell command, like whoami, in vim.

Because the rocket equation is brutal.
A rocket is almost entirely fuel some structure and a minuscule amount of payload. If you want to save fuel for for relanding you need to take less payload or accept a lower orbit.

If we look at Falcon 9, the payload to geostationary transfer orbit^* goes from 8,300 kg when expended, to 5,500 kg when landing on a barge or 3,500 kg when landing on the launch site.

* meaning the payload needs an additional stage to enter geostationary orbit