Is the lav/tub on 1-1/2" or is that 2"? If you used 2", you could have wet vented everything in that bathroom through the lav. I believe that Ohio is on IPC. If so, the distance to vent for the toilet is unlimited.
For the vent with the belly, it should work in most cases (if it stays dry), but inspectors won't like it. It could fill up with rain water or condensation and form a trap, making the vent useless.
I also agree with the others on the structural issues. Those notches are not allowed. It will be especially bad if you are going to tile the floor and the tile/grout will crack with the floor movement.
On the toilet, make sure you get the center on the flange 12" from the finished wall (account for drywall and tile (if wall will be tiled)). If you are short, you will have a harder time finding a toilet.