The end float must be set first, and it will be almost impossible to find the sweet spot of the worm once everything is together. The sweet spot is small, and barely perceivable on the bench. The added resistance of the bushing (which is very small) is greater than the sweet spot.
If you had to back off the end cap bolts to be able to turn the shaft/wheel, you don't have enough shims -in other words not enough end play. The end cap is prone to distortion from over tightening with too few shims between it and the housing. Once bent, it has a greater tendency to leak the oil that needs to be in there for normal use. If you decide to use some sealant between each or any of the shims, the amount of sealant that doesn't squeeze out will add to the thickness of the shim, and increase the end float. Since you had to back off the cap screws, it sounds like the 14-16lbs was directly pressing against the bearings, instead of having tension between the cap and housing. The end float is the space left over after the cap screws are torqued, between the bearings and races. As you have seen or can imagine, too little end float can make the wheel impossible to turn. Excessive end float will cause excessive steering wheel float -meaning the steering wheel will have to move a far amount right or left, before any of that motion is transferred to the steering. The end float is a delicate balance and worth the time it takes to set properly.