To properly display
$day.maxSolarRad.xxx tags will require you to add the field
maxSolarRad to your database schema.
maxSolarRad is a derived observation that is calculated by WeeWX and added to loop packets and archive records. The current
maxSolarRad value (ie
$current.maxSolarRad) can be displayed without any change to the schema, but aggregates or plots require WeeWX to be archiving the underlying data. If you want to go ahead and add
maxSolarRad to the database schema refer to the
Adding a new type to the database section of the
Customization Guide.
As for the other issue with the missing forecast data I don't use the Exfoliation skin nor do I use the NWS forecast so it's going to take a little time before I can provide any assistance there.