First off, we all need to be on the same page as to the amount of food you are feeding. You will need to figure out how much your "puppy starter" scoop hold and the amount of food you are giving. Since this part of the equation is not know you cannot expect anyone to be able to give you even basic amounts of food to feed your puppy. Please determine how much food in a TRUE measuring cup that you have been instructed to feed your puppy. Is it 1/4 cup, 1/2 cup or a full cup of food.
A 16 week old puppy should be fed more than once daily. If I remember correctly at his age it is more like
3 to 4 times per day. I would think a reasonable amount for a 5 lb puppy at 16 weeks would be around 1/8 to 1/4 cup of food per feeding. Feeding this amount 3 to 4 times per day should be an acquitted amount of food to ensure he is being nourished properly.
Your puppies weight has to do with genetics and not the amount of food you are feeding. If he is now 5 lb and is only 14 weeks old he is probably going to be in the 10 to 11 lb range as an adult. Feeding him less is not going to stop him from growing it will just give you a malnourished dog and I am sure that is not what you are trying to achieve.
Here is a chart from the Science Diet website with a feeding guideline according to weight and age.
Puppy Small Bites - Dry If you look at the chart you will see that a 14 week old puppy should be given 7/8 cup of food. You can spread this amount out over several feedings during the day. Always make sure you have water available as well.
As for treats, it is not a good idea to feed too many treats. It would be the same as you eating cookies and candy all day. Just not a good idea. A treat should be very tiny and ideally no larger than one bite.