ADCTH component of offhand - do main hand attacks benefit?

Grim Dawn Classes, Skills and Builds
1

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)

2

Only skills that use offhand attacks will see the ADCTH.

3

Thanks!

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

4

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