Slow learner. Kindly help me in this!

My nephew is very slow learner in studies. He turned 7 recently, he cannot speak clearly and unable to write alphabets properly. I took him to a doctor and he tested his IQ and it was around 82 which he said is below average. Apart from studies he is active in everything. His energy levels are always high in other work. For example:- playing with a random chord and lost in his imaginations. He is very inclined towards sports and enjoys his time in park but he hardly recognise the right or wrong while playing and get injured most of the time. His father (my brother) beats him everyday and sometimes it's brutal which will only add adverse impact on this little kid. I'm not sure what this problem is and how to rectify it. Kindly help me in this regard. Many Thanks