Common denominator of all three issues is bad PRs. You don't say much about company code review process, the central question being, "Who has commit authority?" Clearly the problem child should not.
If it's only you trying to block a merge, perhaps deputize others to co-review. Hearing your same objections from multiple others could make them harder to ignore.
If it's only you trying to block a merge, perhaps deputize others to co-review. Hearing your same objections from multiple others could make them harder to ignore.