As you pointed out, in the early 50's he predicted that Venus would be much hotter (specifying the temperature that would be found within 35 degrees) than can be accounted for by "greenhouse" effect at a time when "astronomers" and "planetologists" were confident that Venus was covered by water oceans and temperatures only 50 deg. F. above Earth's, accurately described the chemical makeup of the atmosphere of Venus that was later corraborated by probes when most astronomers and planetologists were convinced that Carbon Dioxide (actually almost non-existent) would be the primary component, and that they would find some strange things about the actual rotation of the planet... and we find that not only is Venus revolving retrograde, it is apparently tidally locked on Earth!
More and more archealogical anomolies are being found that calls our current orthodox chronology into question.
It seems to me that the test of any theory is how well does it predict actual events. Using this as a criteria, Velekovsky seems to doing all right.