Fixes and improvements in docs and schema from MSv4 review, batch 326 328 334 343 344

[FedeMPouzols]

This addresses the following MSv4 review issues, which didn't seem to require further discussion:
Fixes #326
Fixes #328
Fixes #334
Fixes #343
Fixes #344

Made this combined branch and PR merging together the respective branches of the issues listed. I could also create individual PRs.

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Note well:

This contribution is made under the current ALMA software agreements. 
(c) European Southern Observatory, 2024 
Copyright by ESO (in the framework of the ALMA collaboration)

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