Hi Pilgrim. Here's my shot at it:
The house in the country could represent a frame of mind, a new philosophy of life, or a new way of thinking that you are attracted to and have decided to move into. This way of thinking is based in "God's way" (being in nature, being made of wood) as opposed to "Man's way."
The ex-wife walking in the front door and smiling: Have you recently had the opportunity to spend time with her? It sounds like your dream is wanting her to be with you in this new house. Perhaps it is a dream that is healing you of old wounds.
The herd of horses in the back: Something being at the back door, or at the back of the house could represent issues from the past, or it could be suggesting some intimate soul-searching, as only close friends come in through the back door. It might also mean that the answers you seek are not obvious as you'd like them to be and will require some extra effort. The windows represent enlightenment.
The horse entering the house and passing between you two: First of all, the horse just kind of magically passed through the wall/window to get into the house. That might mean that your rational mind doesn't understand how a certain situation could ever happen, but it does happen. Perhaps the horse represents issues that are "between you." Probably the issues that led to the divorce. Choosing not to be afraid of the thing that you have feared in the past is a positive step. You are facing the issues, at least deep in your soul, perhaps not fully in your mind yet. The dream might also be informing you that fear is what kept you from dealing with these issues in the past. (That's why it used an animal that you're afraid of.) Maybe you didn't even know that fear was motivating you before, but... now you know.
You "turned it around," meaning that the issue/s that were once negative for you have been/will be turned around for something good. This is also indicated by the fact that the horse became pure white, a color of peace, purity, and enlightenment. A white horse in traditional literature often represents a message of peace-- usually peace that is bought through struggle and ultimate triumph.
What do you think? Does that come close?
