Respirations defines the act of your lungs opening and closing, in other words just breathing. On a newborn baby in your case the average rate of respirations (breaths per minute) it should be around 40-44 respirations per minute.
No. you should take him to the hospital and see if he has any medical problems. I have never heard of a 3 year-old throwing up after playing. am sure you are concerned parent and you have a good reason to be, this is definitely not normal.
The average weight for an 11 year old depends on certain factors. 1. Male or Female. 2. Height 3. Build. 88 lbs. is about average for an 11-year-old girl. (***Disclaimer: Please embrace the concept that there is no such thing as 'normal')