ADDISON COUNTY — Three hundred sixty callers dialed in on Tuesday night for an hour-long Addison County telephone conference with Vermont’s lone congressman, Peter Welch. Fielding questions from county residents, the Hartland Democrat tackled issues ranging from those far afield — like the oil spill in the Gulf of Mexico and the wars in Iraq and Afghanistan — to those closer to home, including concerns about energy efficiency, the effect of health care legislation, and dairy industry and immigration reform.