Do wider tires wear better?
While I'm not a road biker, I can speak from experience with mountain bike tires. The first spot to wear is the center of the tread. Why? It's the part that is ridden on the most. Increasing the width of your tire with increase the contact patch (the part of the tire touching the ground); therefore, your wear is going to be the same because that contact patch is still hitting the ground the same amount. That said, the amount of pressure put on that contact patch can change due to width, as the mass of the bike and rider is spread across the larger area.

Tire pressures can affect your contact patch as well, lower pressures allow more of the tire to hit the road or trail. This means your going to expose more of the tire to wear, increase grip (in the case of mountain tires, don't know about road so much), and increase rolling resistance.

Other wear patterns will depend on the type of terrain and riding style. If you ride on very smooth asphalt, you probably aren't going to wear through a tire that fast, but if you ride on loose, rocky, beat-up roads, that's going to eat at the rubber much more quickly. Similarly, if you do more straight-line riding you're most likely going to see the center wear quicker than the sides, but if you turn more (or skid a lot when braking into turns) you can wear down the sides quite a bit too. There are other environmental factors to consider as well (heat, humidity, etc.) that can affect tire wear, but those are much harder to quantify.

I would look more into finding specific types of tire, maybe ones that address the hard/softness of the rubber instead of looking for wider tires. Also try experimenting with tire pressures outside of what you're doing now. If you want some hard numbers, I would recommend looking at specific tire manufacturers who may have testing data available and estimated mileage charts for certain riding conditions.