Thanks for the quick response.
1) Your CSS suggestion fixed the infowindow size issue.
2) The old manual links to the thumbnails were removed but the problem remained as you thought it might as WordPress does indeed leave out the px in the width and height settings. Setting the .mapp-thumb style as you suggested fixed the problem.
3) The padding issue is resolved in 2.38.5
4) The ‘zoom’ issue remains in 2.38.5. The ‘zoom’ and ‘direction to’ boxes don’t stay unchecked after ‘Save Settings’.