Size is not something to be considered when making decisions about school. Although we have an emotional response to sending our small kid to school it is really not important at least in the first years.
It really sounds like the screener didn't have a very good grasp on development. A five year old who scores 4.5 to 5.5 sounds entirely normal. If he had scored 3.5 to 4.5 maybe there would be reason for concern or to test with a proper test. As for not knowing what you do for a living that would be pretty common. Some jobs are easy for the kids - she is a cook, she cooks but engineer and lawyer are a bit more complex. Unless your husband specialises is bridge building and talks about it a lot i wouldn't expect him to know.
