Three things will help you with your 2014 E450 chassis. If after you do all three and you still are not satisfied, then there is another list. But do these first, then move on from there.
1) The right tire pressure with consideration to the weight on your front tires.
2) A front wheel alignment done with your rig loaded up as if on a trip
3) A heavy duty steering stabilizer (which you are researching)
Our 24 foot rig with 158" wheel base has a Safe-T-Plus steering stabilizer and we like it very much.
As you have learned, the stock steering stabilizer provided by Ford is ineffective.
The worst handling class-C rigs are the shortest ones with huge rear over-hangs behind the rear axle. The longer the rig, the more stable it is on the road. The sweet spot seems to be an extended wheel base around 200" and 26-27 over-all length.
