I'm finishing the attic space and need help connecting a shower and toilet together. A 3" drain and hot/cold supply lines have already been run up from the crawl space but pop up close to the eaves of the space. So I have got to come across a few joists to my fixtures. Because of the head room, the best fixture layout option is shown.

I've attached a sketch of the layout and have the following questions:

1. Do I need the extra shower vent line? The shower waste line will be over 6' long and code says I need a vent - right? Adding the extra vent line would really be a hassle to deal with.

2. How best do I get the drop in the 3" toilet line? Using 90's at each end would make a flat connection with such a short span.

3. For connecting to the 3" and keeping everything below the 10" joist, I plan on using a 3" 90 with a 2" side inlet. Back to question #2, are these the right fittings?

4. I've got 3/4" t&G plywood subfloor and plan to have tile installed. What will be the remaining thicknesses so I can plan the closet flange height correctly?

All PVC.

Thanks for the help.

Sorry - first timers problem with the sketch. Here is the full sketch

Thanks