Start for scratch.. again
If the Wireguard client is not used as default routing and you create policies to selectively use the Wireguard client, make sure your settings are as following (three dots on the line imply other options can be listed in the section as well). Make sure that the policy mentioned below is at the top of your policies list.
The author has his own thread and is active. The ReadMe has troubleshooting tips and ways to push details to the project.
I can see that keeping the Omada untouched is a primary goal and that working on the WAN facing OpenWrt hardware is where you'd like to concentrate.