I’m no geologist, but I’d be rather surprised to hear of a volcano that spits large volumes of material out at thousands of feet per second (delta-V necessary to transition from a lunar orbit to Earth). I would think it’s more likely that if there was a correlation between a large impact on Earth and seismic activity on the moon it would be Earth’s seismic activity that had a larger influence on the moon. Again, not in the field so take this all with salt.

With low gravity and no atmosphere, I can imagine stray rocks escaping into space.

I'd be real surprised if they were of any significant size though.

Isn't it more likely that volcanic activity on the moon was caused by meteor impacts? Maybe there used to be a lot of asteroids in Earth's orbit. The moon took a lot of the hits until the big one slipped by killing the dinosaurs.

Not necessarily. There are many types of volcanoes, and shield volcanoes aren't as violent... they ooze material rather than explode like a cinder cone. That lava wouldn't have enough momentum to go very far.