15 inches from outside edge of tub to center of toilet flange.
Center of the hole to the back wall behind the tank. Should be 12 inches.
The average spacing of shelves in a linen closet is 15 inches apart. The width of the linen closet usually 36 inches.
The standard depth of hanging closet rods is 24 inches. The standard width is usually between 72 to 96 inches. The closet height is generally 84 inches.
A standard closet is 27 inches front to back. It is also 40 inches wide from side to side.
Your toilet should be roughed in from finished wall to centre of outlet flange at 12 inches. This will keep the tank on most models about one inch from the wall.
12 inches from finished back wall to center of toilet flange.
Before hanging Closet Maid shelving you will need to measure the closet and purchase materials needed. ShelfTrack should be installed on studs where possible. Where studs are not possible, you should use toggle bolts to ensure secure installation. Once the track has been installed no more than 24 inches apart, then hang shelving.
PVC I assume. If you can get to the pipe, cut it and replace a short section along with the flange. There is a flat steel repair ring that could be screwed down on top of the flange. There are flat repair plates for cast iron flanges that might work. They are about 6 inches long, curved the same radius as the flange and slide under the old flange to give you some place for the anchor bolts to slide into.
Because there are no building codes governing closet sizes, there is no such thing as a standard size closet door. There isn't even a standard style. Some are prehung, others are sliding doors and still others are bi-fold doors. Some common sizes for bi-fold style doors are 24 inches by 80 inches and 30 inches by 80 inches.
Making allowances for the flange and curvature, it is about 120 Imperial gallons.