Baseboard Part Deux

I think I have solved the baseboard problem.

I took my construction pencil and laid it on the floor with the lead up against the baseboard. Starting at the left end where the gap was really big, I drew the pencil along the board and created a cut line that followed the contour of the floor. 

I then used my jigsaw on the board, cutting right to the line, which created an arc that presumably matched the bow in the floor.

It worked! The board now sits much more snugly and flush against the floor. I ended up doing this procedure twice and I have gotten the left side to where the base shoe covers the gap. I might run it one more time to really snug it up.

I'm happy.