As a multiple Dakota owner, 2WD and 4WD, I can state that your braking should not be lacking. Your vehicle has brakes designed to be sufficient to stop the vehicle and a 4,500 trailer in a reasonable distance. I have tested this personally, many times.
The front brakes do most of the work on all vehicles. Dialing in more rear brake will just invoke the rear anti-lock brakes (standard on your Dakota) more often.
First, you need to look at your front brakes. In particular, were the correct semi-metallic pads used? If ceramics, organics, or "race car" performance pads were used instead, I would go straight back to OEM Replacement grade pads. If in doubt, buy Mopar parts from the dealer. Of course a fresh set of rotors, properly dialed in with minimum runout, broken in properly to avoid pad imprinting, will also help.
Next, look at the pad tracks, which are extensions of the knuckle fore and aft of the caliper, where the pad ears ride. Are they lubricated? Are they clean and have no grooves? (You will have to remove the caliper and pads to determine this). If grooved, the pads are locking in place and tilting instead of sliding during braking. If so, dress them flat with a file. (This may sound horrid if you've never seen this style of Mopar brake, but once you see what I mean, you'll understand). If unlubed, lubricate them with a brake qualified lubricant such as SilGlyde. Also check the pins for rust and sufficient lubricant.
Next, check your caliper. Does the piston move out smoothly when the brake is pressed? (Have someone GENTLY and SLOWLY press the brake pedal part way down, with the caliper removed, resisting the piston with your hands). If it's crunchy, the caliper needs to be rebuilt or replaced.
Second, look at your rear drum brakes. Use the Star Adjuster to move the shoes in a bit and easily remove the drum. Wash down excessive dust with Brake Clean onto newspaper, bundle up in a plastic bag while still wet and discard. Lube the contact points between shoes sides and the backing plate with a VERY SMALL amount of brake qualified grease such as SilGlyde. Once reassambled, the Star Adjuster can be used to bring up any slack in between the shoes and the drum. Expand until they make contact and then back off one notch. This adjustment is important to giving you quick response and optimal rear braking.
Third, your hydraulic system. If your brake pedal feels spongy or goes low to the floor, then you need a brake fluid bleed. If this doesn't help or you need to do it again soon, then there is a leak. I would look first at the brake Master Cylinder.
If braking is there but only if you push the pedals very hard, then the Brake Booster is not doing its job. Check for vacuum leaks, and replace the booster if necessary.