Thanks for writing your query.
After reading your post, it seems that your child is having viral or seasonal cough.
You should get him examined by a Paediatrician. Antiallergy medicine like Levocetrizine will be helpful in curing the runny nose and cough. Give medicines under medical supervision only.
Children have faster heart beat as compared to adults. Also record his temperature as fever also increases heart rate
can occur during coughing due to reflex. It is more commonly seen in children and is a normal phenomenon.
Pain in abdomen can be due to muscular pain
due to excessive coughing or vomiting.
Make him wash his hands before and after meals as this habbit prevents a lot infection from entering our body. Also give him fresh fruits and vegetables as they increase the immunity of body and decreases the recurrance of infections.
Also get his blood investigated for Complete Blood Count
(CBC) and Absolute Eosinophil Count
I hope this is helpful to you.