Drain Layout Question

I am getting ready to bust into an adjacent closet in my existing bathroom to make a walk in shower. To get the new drain location I will have to make a 135 degree turn out of the existing cast iron drain stub (see sketch).

Can anyone tell me if my proposed plumbing layout in the picture below looks OK? Are there any issues making this kind of turn in my drain line? FYI, I am slab construction so I am trying to minimize the amount of slab I have to remove to route this drain line.



Shielded couplings can be used like this.

Duplicate thread in shower and bathtub forum...
With additional information...

https://terrylove.com/forums/showthread.php?t=22049

drain

Here, the Fernco would not be permitted and the line could only go 4' without a vent, but the 135 degrees is okay, although I might want to do something to make it as small an angle as possible.

HJ- if I tie a new vent line right after the p-trap would this meet code requirements? This line would still run ~24" under the shower bed as shown in the revised sketch below:

drain

Is the existing vent in a brick wall? If not, why not run the vent back to that wall and connect it to the existing vent at the proper distance above the floor?

HJ - the existing vent is the exterior wall of the house. To get the new vent line over there I would be busting up the foundation in the area of the footer where it is extremely thick (12"+). I could go that route, but honestly I am concerned with demo of the slab that close to the exterior, I'm not sure how that may mess with the integrity of the slab in that area. This house is 50+ years old in Houston soils so the slab needs all the lovin it can get!

Honestly, this is a single story house so in my opinion it would be much easier for me to make the new vent line where I have shown it, I have clear access above this bath in the attic so getting the new vent line up through the attic and out the roof with some new flashing will be much easier than tying into the existing vent.

With this new information do you agree with my approach? I'm young, first time owner, so if I'm way off base here please let me know...I want to do this the right way the first time!