ADCTH component of offhand - do main hand attacks benefit?

As title, if I put a seal of blades on my shield, will main hand attacks benefit from it (devos, cadence, etc), or only skills using offhand damage (1h forceweave, half of blitz, horn, etc)

Only skills that use offhand attacks will see the ADCTH.


ADCTH on other items (restless remains, solael pants, etc) will benefit both main- and offhand attacks, right?

On weapons, only the weapon used in the attack benefit from ADCTH. On jewelry/boots/helmet whatever you name, it will work afaik.