My 30lb son (2.5 years old) was given a dosage of 7.5ml twice a day of amoxicillin (400mg/5ml) for ear infection. does this seem right?

Yes: This the right dose for twice a day according to the weight and diagnosis given. for three times a day, not practical, the concentration is less but total amount /day is the same. Please take the full prescribed duration even if your child is better

TOO HIGH A DOSE: The maximum dose for a 30 lb child should be 3.75 ml twice a day (or 2.5 cc 2x/day), so he's taking 2x as much as he should. However, I question the need to give antibiotics at all. A thorough review of research shows "antibiotics were not very useful for most children with" acute otitis media. See http://tinyurl.com/jbvdt2s However, antibiotics disrupt the microbiome. I wouldn't give to my kids!

80mg/kg: American Academy of Pediatrics has been advocating an 80 mg/kg/day of amoxicillin for many years now. At 400mg/5cc this comes out to 5.5 cc by mouth twice a day. The dose is a little high, even by our standard of rounding. A teaspoon and a half is 7.5 ccc. Your provider seems to have rounded this up, perhaps due to this age notoriously spitting up medicine. Ask her.