This dream appears to be rich in emotion and symbolism. Let's break it down:

1. Setting (Work at a Storefront): Dreaming of a workspace, especially when you work from home, may indicate feelings of being out of your comfort zone or dealing with the pressures of your current life situation.
2. Your Girlfriend and Her Ex: The presence of your girlfriend's ex can signify unresolved feelings or insecurities in your relationship. The playful interaction in the parking lot might represent feelings of jealousy or fears of comparison.
3. The Minivan: Vehicles in dreams often symbolize the direction of your life and personal control. The minivan, which is not her actual vehicle, could suggest feelings of instability or uncertainty regarding your girlfriend's past and how it affects your present.
4. The Parking Struggles: His difficulties in parking the van may symbolize a lack of direction or control in your relationship or in your life. This could reflect your anxieties about how well things are going.
5. Physical Confrontation: The fight represents underlying tensions or conflicts that might be present in your life. Your reaction to confront him shows a desire to assert control or protect your relationship.
6. Guns as Symbols: Guns often represent power, control, or the potential for harm. Showing your own gun can indicate a feeling of needing to defend yourself or your relationship, suggesting a struggle for dominance or security.
7. Telling Your Girlfriend to Cease Communication: This part of the dream likely reflects feelings of wanting to protect yourself from potential emotional pain. The argument about this decision signifies a conflict between your protective instincts and the reality of your relationship.

Overall, this dream might be reflecting insecurities, fears of losing control, and the complexities of your relationship dynamics. It could be beneficial to communicate openly with your girlfriend about any feelings of jealousy or insecurity you may have. Addressing these feelings in a constructive way can help strengthen your relationship and resolve any underlying tensions.