I think he's strong, possible even be strong enough to be the final boss. I don't trust him after the events of Volume 12 and 15.
Woodman's strength huh, It's really hard to say right now, because things were left deliberately vague. He managed to fight to fight against Westcott to a standstill, but out of the two, he took more injuries than Westcott. Plus, Westcott couldn't use <Beelzebub>'s full powers due to Nia's interference.
There's a description of him taking something resembling a golden dog nametag before the battle, I think his powers are more Realizer based, more akin to a Wizard than any Spirit powers that a lot of people have been speculating. Later in the volume, Origami pulls out something that was described as resembling a silver dog nametag to summon <Bryhlider> from a distance.