In order to use community tokens you need to extend forceCommunity:base and should work.
In order to debug your component and check if everything work currently you can open Inspector and check your component in the list of styles you should see something like
this would allow you to verify that CSS tokens are ...
No. Dynamic Forms are available only in Lightning App Builder.
Here's the mention of this on the Winter '21 release notes (emphasis mine).
It adds the ability to configure record detail fields and sections inside the Lightning App Builder.
For 2) at the moment, LDS only detects changes done through Aura, LWC or the standard salesforce UI (which are lightning components indeed). That means that your change, being done through an API won't be detected. There's a feature salesforce is working on to overcome that --> see LWC Force Refresh Wire getRecord
For 1) you will have to use $A....