A.G.
My husband (49 years old) has extremely low testosterone. I don't remember the latest number, but he gets tested every 3 months. He was treated by a general practitioner first, and tried weekly injections, but his numbers didn't improve. Now he is seeing an endocrinologist who did tons of tests to rule out all sorts of possible causes, and determined that my husband is in perfect health aside from low testosterone (he's always been a good weight, good cholesterol/blood pressure, doesn't have any mood/depression issues, etc.).
Now his endocrinologist is having him give himself weekly injections, but at a different dose than he was getting before. We'll see how it goes.
He hasn't had any side effects from the testosterone shots at all. On the first day, he says he feels a little more energetic, but doesn't feel any different after that. He's always had a lot of energy anyway, though, so I don't know if he would really notice it if it did give him energy. He hasn't been hurt in a long, long time (knock on wood), so I don't know about the healing time. Also, he's a very easy-going, happy guy, so I don't know about it improving mood. It certainly hasn't hurt his mood, and he hasn't had any issues with rage or anything.
I'm glad your husband is seeing a doctor, and hope he gets the help he needs.