ACR: clean up codebase, add error handling and comments

[anamnavi]

This PR:

• creates a static instance of the empty FindResults instance, so that it can be returned in all error cases for the overriden methods
• add error handling, for async methods these will throw, for non-async methods these out an ErrorRecord instance
• categorize methods into more defined regions, for easier reading
• add summary comments before each method

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