Question regarding stack vent layout for remodeled bath

[SergeiS]

Hi, I'm in process of my bath remodeling. Bath is located on the second floor. I'm converting the standard toilet/tub kid's bathroom to walk-in shower/toilet bathroom. I want to move the toilet to the new location and use the space that was occupied by the toilet for the shower. During demolition I discovered that my waste stack right in a middle of my bathroom floor. I have a very limited access to relocate the 3" waste pipe. The goal is to hide the pipes inside the existing wall and floor cavities without demolishing ceiling below. I drew a pipe layout to explain my situation. This waste stack serving only 2-nd floor bathroom. No others plumbing fixtures are connected to this pipe. Existing 3" waste stack has been offset-ted w/ (2) 45 deg. fittings. I connected 3" drain from the toilet and 2" drain from the shower to the 45 deg. section of the waste pipe. Shower trap is vented and connected to the vent stack above the ceiling. 3" vent stack goes vertical and through the roof. Do you see any problem with this layout? My concern that new toilet pipe is not properly vented. You advise would be greatly appreciated! Thank you! My location is under Illinois Plumbing Code.

 

[SergeiS]

Well, I still have some concern regarding the layout. The pipe between the toilet and shower connection could be treated as a wet vent. However I'm technically connecting shower to the toilet vent pipe which is otherwise prohibited. I come out with a different layout and made connection from the shower drain pipe below the toilet connection. It will involve some modification to the wall below ( need to add 3" to accommodate parallel piping).
What do you think? Does this layout work better? What fitting should I use to connect toilet branch to 45 deg. pipe. San tee or wye & 1/8 band as shown? Wye required on vertical to horizontal and not permitted from horizontal to vertical. Now is 45 deg pipe is treated in this case?

Thanks for all your advice!