Hi Zacks Mom,
My son too had terrible knee and leg pains for most of his young life. He would scream in pain and cry and I would never know what to do for him. I to took him to the dr's and specialists but in the end they said the same thing it was growing pains. For my son they were right. He was growing faster than his body could keep up with him. Where most children would grow a little bit he would grow an inch. He was 6ft by the time he was 13 and is now 6'4 at 16. I would massage his legs and I would i put him in the spa bath and give him panadol until a physiotherapist suggest that before going to bed and starting his day he do stretches to get his ligaments and tendons to grow with his bones. He would simply put a thick book on the floor put the tips of his toes on the top of the book then push down with his heels to the floor. This did help him immensely but the pain was still there at times. The temperature is due to pain and when in pain your BP goes up naturally. Also watch what he eats. Limit his starch intake try no white breads etc. The blood test results are a good sign that there isnt anything too serious wrong with him but if you are concerned still keep demanding blood tests or a bone scan.
I am sure Zack will be ok.