EHsvc.dll is packed with Themida. I was under the impression I'd need to patch it, though I guess I didn't end up needing to. It was a long run at the computer and my memory is fuzzy (though I have before/afters of anything I patched for comparison).
In the end I patched Engine.exe (to ignore the various return codes from EHsvc.10()) and autoup.exe to just skip updating (easier than patching Engine.exe to skip updating).