DEAR ABBY: I am very close to my 19-year-old son. He is kind, sweet and big-hearted. He has learning disabilities and the maturity level of probably a 15- or 16-year-old. Naturally, I am protective of him. He had one girlfriend during his senior year, and when they broke up after four months, he was beyond devastated. Since then he constantly talks about how lonely he is and his desire to be in a …