Place venison in a large bowl. Stir in red wine, 1 teaspoon salt, and black pepper. Marinate for 10 minutes. Remove the venison; reserve the remaining marinade.
Heat olive oil in a large skillet over medium heat. Stir in venison; cook and stir until browned, 5 to 7 minutes. Transfer to a plate. Drain and discard any remaining grease. Melt 2 tablespoons butter in the same skillet. Add onion and 1 pinch salt; cook and stir until onion is soft, about 5 minutes. Add garlic; cook until onion is translucent, about 4 minutes. Transfer mixture to a plate with the venison.
Melt 1/4 cup butter in the same skillet over medium heat. Whisk in flour; cook and stir until lightly browned, about 4 minutes. Slowly whisk in beef stock and water. Bring to a boil, stirring constantly. Reduce heat to medium-low. Pour in the reserved red wine marinade, Worcestershire sauce, mustard, and red pepper flakes. Add the venison and onion mixture. Cover and simmer, stirring every 20 minutes, until venison is tender, 1 to 2 hours.
Stir cream of mushroom soup and cream cheese into the skillet about 5 minutes before serving. Season with salt and pepper.