It sounds like the number you are talking about is the hemoglobin, which is a measure of a protein that is found in red blood cells. If his number is
7, that is low, and it sounds like he may be at the level of needing a blood transfusion.
The average hemoglobin level for an adult male should be around 13.0 to roughly 17 gm/dl. However, "normal values" really depends on the lab that processes the blood test (the normal values are listed on the results).
It sounds like the bigger issue for you is getting information you need from your family. Since you are the daughter-in-law, it is difficult with the privacy laws to obtain medical information about your father-in-law. Perhaps your husband can ask his mother if he can speak to the medical team about his father.