Houseplants often lose a few leaves when brought indoors for the winter as their leaves adjust to a different light level.  A huge change in temperature also will cause leaf yellowing and drop, if, for instance, it was starting to get chilly outside and the house is much warmer. Best to bring them in when outside and inside temperatures are similar. 

Water is often not absorbed by soils when they have been allowed to get entirely dry.  This condition is called 'hydrophobic, and means the soil actually starts to repel water.  When soil gets that dry, water runs off and down the space at the edge of the pot (the soil has contracted and doesn't fill the pot now), and never is absorbed by the soil. It sounds like that has happened to your pothos. Don't let soil get that dry. 

Once soil get overly dry, hard, and shrunken, you can either:

1). water by pouring a little bit at a time, over and over, letting it gradually absorb more and more until the entire pot of soil is once again wet. This is pretty tedious. 

Or 2). submerse the entire pot in a bigger container of water and let the water saturate the soil. This is a lot faster process. 

The new potting soil you used may be more prone to this condition. 

The speckled plant photo also shows a build-up of fertilizer salts (white grains) on the surface of the soil. Repot with good quality potting soil.

Ellen