Yes, it is a science, proved beyond doubt by the great genius of  Prof. K S Krishnamurti.
He successfully and accurately predicted thousands and thousands of events in the lives of his consultants, not only with day and date, but many a times, with exact hour and minute of happening which have come to pass surprisingly true.
 

That’s due to insufficient and outdated methods and tools employed by traditional astrologers. Late Prof. Krishnamurti, successfully demonstrated that all the rules and theories given in  the scriptures by our ancient rishis are not effective in today’s world. They are general in nature and not sufficient to meet the  specific requirements of the present day necessities.
He did researches for over 40 years and invented new and effective tools which can be universally applied to obtain desired results.
 

No. Because the chart of the native shows, as explained by Hindu scriptures, the good or bad deeds one has done in the previous birth and the results one has to enjoy during present birth. However, one can minimize the bad effects by proper propitiation and good deeds when he knows through astrology what is in store for him.