Converting stand-alone shower and laundry in garage, into a half bath with laundry

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Hi. I am planning to add a toilet and a sink in my garage next to the laundry area. The below slab plumbing is already there since there was a stand-alone shower in the garage. I just want to switch out the showers drain into laundry pipe and use existing stand pipe plumbing for macerator vent.
All lines are 2" so I would use a Saniflo Saniaccess2 macerator pump for the toilet and sink.

The main drain is located 50' away, and the closest 3" drain is 40' since it's on the other side of the house.
Also, the access in the ceiling is very poor because I have a vaulted ceiling. Plus, the vent pipe is inside the exterior wall, so the space is extremely tight.

I drew a plumbing layout, sorry for the perspective but Im not good with technical drawings. This is how I was planning on doing it:

Toilet laylout.jpg

And this is a sketch of the main line layout through the house:


Now, I am not sure about 3 things:

- Is the vent tee (old stand pipe drain) at 10" above the slab fine, or do I need to put a new one higher?
- Where should i tie the macerators discharge line? I was thinking either the drain below slab after tee, or into existing vent tee, while putting another vent tee above it.
- Does the stand pipe need a separate vent if I would tie the macerator discharge below slab?

This is how I was thinking of doing this:

Hey, wait a minute.

This is awkward, but...

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