Solar activity levels have increased since the Maunder minimum, and the correlations between solar activity and temperature here are not bad. The mechanisms (likely something to do with the increased solar wind interacting with our atmosphere directly, or by interacting with the Earth's magnetic field changing the cosmic ray flux into the atmosphere) are obscure, but this is one case where correlation and causation are probably one in the same. That is, the possibility of anything on the Earth being able to affect the Sun is so remote that the correlation must mean the causation comes from the Sun.

You are correct that the actual temperature rise of the Sun when more active is fairly small, something in the range of a few tenths of a percent if I remember correctly.

Recent paper you may wish to look up on this subject: "Phenomenological Reconstructions of the Solar Signature in the Northern Hemisphere Surface Temperature Records Since 1600" , Scafetta and West, in Journal of Geophysical Research, v. 112. If nothing else this paper shows up the flakiness of ALL the models of solar forcing presently in play.