"Breaking it down" means to take something complicated and reduce it to a number of simple parts. Charley is joking with his mom, poking fun at her because she approaches the situation in a way that is overly analytic for a romantic relationship. She concludes that an attractive man that is still single is most likely someone who runs after women and won't commit to a relationship. In other words, she breaks down her observation about this man into a number of conclusions that account for what she's seeing but are not necessarily true. Most likely, she is protecting herself from rejection rather than allowing the chance of a real relationship (her words more or less indicate that). Charley uses the progressive because he's talking about something his mother is doing as if it is happening at that moment (even though it happened immediately before he said that). It's normal in English to use the progressive to talk about something someone has done in the very immediate past, though this is a very colloquial and informal way of talking.