This is a tough question, since the reader gets very little information about Boo's thoughts and actions during the course of To Kill a Mockingbird. The love in Boo's own household is certainly not evident, though his father must have somehow considered it best for his son when he locked him away inside the Radley House for decades at a time. When both of Boo's parents die, his brother, Nathan, comes to live, but there is little evidence that Nathan loves Boo; rather, he comes to serve as Boo's protector--his warden. Perhaps Boo has witnessed love in the outside world as he peeks through his windows, watching the children play; seeing them hug Atticus on his way back from work; and, possibly, catching a glimpse of Scout and Dill sneaking a kiss. Boo's own actions toward the children--leaving them gifts in the knothole, mending Jem's pants, and warming Scout's shoulders with a blanket--show that he has a loving nature, but how he has learned it is a mystery.
Boo's knowledge of courage may have also come from his limited view from his windows. He may recognize that it took courage for the children to break the ice by attempting to make contact with him. Boo must have known about his reputation for being the "ghoul" of Maycomb; no one else had the courage or caring nature to visit him (aside from the doctor occasionally), so he may have admired the spunk shown by Jem, Scout and Dill when they ventured onto the Radley property. Boo probably didn't consider his defense of the children during the attack by Bob Ewell as courageous; he saw it as an act of love: coming to the rescue of the only two neighbors who ever tried to befriend him.