those are all good concerns. I don't think air circulation would be too much of a problem for my particular case. Too much wind have been a problem at my plot. I have more problem with wind stunted plants than fungus. since I'm planting them as windbreak I think they will get plenty of air circulation.
Too much shade might be a serious problem thou. I think I might have a solution to it. I'm planning to plant two rows of tomatoes side by side but staggered. So the tomatoe plant and the nearest 2 tomatoe plants form a triangle. The spacing between them would be around 3'. Then run one bean pole diagonally through each tomatoe cage, making sure to secure the cage at two points on the pole. Then tie the 3 poles at the top to form a tripod and stabilize the whole thing. The tripod would cut down on the shades beans would cast. It might be more work to train the beans up the poles rather than allow it climb all over the tomatoes.
As for too much nitrogen, tomatoes are heavy feeders, I don't think it would be much of a problem. If it becomes a problem, I guess I just will have cut back on the Miracle grow and save some money.