Good evening, I added an attachment that has a crude drawing of what my set up looks like. Bottom line, looking to see if my proposed set-up makes sense and is within code and if the venting is adequate. I appreciate any input and advice!

I am adding a half bath to the main level of the house the new drain system will go into the basement. I have multiple questions so I'll start with the general layout. My toilet will have a long sweep 90 connecting to a 3" drain that will run horizontally 16' to a 45 for 2' then another 45 for 4' then 90 down to the vertical pipe but also need to tie in another 2" drain at this point. My sink drain will be 2" and serve as a wet vent for the toilet. The vent will go straight into the attic and tie into other vent. The drain will go into the basement 90 to a 3' horizontal run to the horizontal toilet drain about 3' down stream of the toilet. 1.. were the sink drain/vent ties into the toilet drain what type of fitting should be used. Its confusing since it's a vent/drain and both runs are horizontal? 2. Were my toilet drain 90's to go vertically into the slab what fitting can I use to 90 the 3" and the 2"?not sure if this will be a sanitary fitting or other. 3. Were I will make the connection to the main sewer line I was told to use a long sweep 90-1/8 on it's back not sure the correct name of the fitting. Then a 2' horizontal run to tie into the vertical pipe. There will be a couple 45 in this to make it line up correctly. Does this sound correct? Why does the wye and 1/8 fitting need to be on it's back? Thanks for any help.