Jodi,
I would ask your pediatrician to check his BMI which is a better indication than actual weight. My 4 year old is 42 inches and 42 lbs. He is in the 90th percentile for height and weight. (A quick check of my chart makes it look like your son is in the 95th for height and weight is 100th or more (not on the chart-- but close). I was worried when he was a baby b/c he was very chubby (cute on a baby...but not so cute when they grow up). My pediatrician told me that as long as the hieght and weight percentiles were within about 5 percent of each other it is fine (i.e. the taller your son, the more he can weigh).
I try to balance treats with healthy food. I am a big believer that children should NOT be forced to clean their plates and that treats should not be withheld for no reason b/c it makes them want them more. If he is active and eats healthy I wouldn't worry about it (sometimes that can creat a problem by itself) and maybe your pediatrican confirming that he is not overweight will help your husband.
Good luck.