The graphics for the springboard don't show up correctly because, unless you do a significant amount of ASM work, the sprite tile shown in the item box is always a single 16x16 tile, and the springboard is composed of four 8x8 tiles. If you reserve a few extra tiles for a full 16x16 springboard in SP1/SP2, then you can make it display correctly.

As for the P-switch not working, presumably that is because all sprites normally drop from the item box in status 08. The P-switch, however, doesn't have any code for that status; it starts out in status 01 (init) like any other sprite, but then it goes directly to status 09 (stunned) instead of 08 (main). So you'd want to use this patch to make it drop in status 01 or 09. Unfortunately, the P-switch also normally sets its color depending on its X-position when placed in the level, so even just dropping it in status 01 most likely wouldn't make it show up correctly. You could, however, use one of the P-switch custom sprites and, with the linked patch, make that drop from the item box instead. Alternatively, you could use one of the "effects" available in that patch (they run code when the item drops instead of spawning a sprite) to spawn the P-switch and set the necessary sprite tables manually.