What can I do to get better mileage performance in a 1999 Dodge 1500 Ram? Also, the dash is cracked in several places, any recommendations on how to fix it?

Fuel booster is a waste of money. Putting in the gas tank an occasional bottle of Techron fuel system cleaner is beneficial. The biggest killer of fuel mileage is a poorly tuned engine and under- inflated tires. Do a full tune up if necessary (spark plugs, belt(s), filters, transmission fluid, differential lubricants, transfer case fluid, etc.). You should be driving around in 2H unless the road conditions warrant 4 wheel drive. Driving around on dry road surfaces in 4 wheel drive consumes extra fuel and wears things out, including tires.

Thanks. This is very helpful. My husband passed and i'm just getting to know these things. The 2H seems to drive ok around town as well.