There is a lot that needs to be done here.
1). That poly under the slab needs to be mended at the end.
2). I would keep everything in 2" and change to 1 1/2" just before the T where the drain and overflow connect.
3). 90's are not allowed unless they drop into a vertical line
4). I think the make bends can not exceed 135 degrees.
5). You need to break up more concrete against the back wall most likely. Get your tub in rough position with the drain and overflow dry fit.