Although I've not experienced it myself (I've alway had separate transformers), I've heard that PW ZW's are affected by multiple power draws more than some others (Z's seem to be better, but they have no whistle/direction buttons). Lionel made the dual-coil TW transformer specifically to prevent the voltage drop - one coil for running a train and the other for accessories.
Just for grins, try wiring your track to D and your switches to C. Chances are the left-side components are less worn, since most operators are right-handed and use the A and B levers. Might not help, but it couldn't hurt!
BTW, with 7 O-22 switches, the 14 lit bulbs would be drawing about 63W, the limit for continuous operation of 1033. Throwing a switch only produces a temporary load, so that won't be a problem. But consider dedicating the 1033 to just those switches.