Patch up exceptional flow

[karnkaul]

facade uses exceptions in non-happy paths to signal unrecoverable errors. This has been set up properly during application bootstrap but not so much in the update / render loops: there are sprinkles of asserts and // TODOs in some places which need to be fixed.

This issue is only scoped to fixing error-related // TODOs and asserts.

AC:

1. Areas of code that need to be addressed have been identified and enumerated
2. Resolutions for contentious / ambiguous fixes have been discussed
3. // TODOs (relating to errors) and temporary asserts have been refactored