Hi Patrick Ladner,
After creating a custom header, the logo, menu, and off-canvas should be fully responsive. You can refer to the documentation below for guidance:
Helix Framework - Responsive Layout
Additionally, I have made the off-canvas responsive for you. You can check the update here:
Preview Screenshot
If needed, feel free to make any further adjustments by following the off-canvas setup.
I have also duplicated the template and set it as default, so you can compare the changes I made.
Let me know if you have any further questions.
Best regards