In my opinion you have installed the wrong fork. The fork you used is what I would call a Lowrider Fork. You've added so much trail to the front end geometry its no wonder it handles poorly Look at the standard Schwinn Springer at the link provided and compare it to the one you have? Note the amount of bend in the main fork legs? http://www.schwinnbike.com/usa/eng/S..._1201_3651.jpg
Also you need to either cutoff the excess steerer tube or add spacers to fill in the gaps between the headset lock nut and the spring anchor and between the spring anchor and the headset top race. But first and formost you need to get a standard Springer instead of the LowRider Springer.