Remodel venting

I am doing a bathroom remodel of my 1979 home and am not sure if I should be looking to make changes to the venting of my bathroom.

The the 3" main stack runs up one corner of the bathroom. From that stack, a 1-1/2" branch splits off below the floor and runs a total of 8' to a P-trap for a shower/tub. Above the floor, a 1-1/2" branch splits off and drains a total of four sinks (2 double sink vanities, back-to-back).

Do I need to make any changes while the room is ripped apart?

I've attached a quick sketch of the situation for reference.

It would next to impossible to circuit a vent back to the stack in either case, but could probably go up through the roof at the end of each run if that is required.

Thanks!

drains

The 4 sinks are completely wrong. You might get by with doing it that way for 2 sinks if done properly, but never 4. And as far as the tub, it depends on how, and where, the toilet connects and if there is a bathroom or anything else upstairs.

This is on the second floor. The toilet was omitted in the original sketch and in researching how it connects in a few minutes ago, I discovered that the stack "jogs" over about 3' between floors. The toilet is connected in the middle of that jog.

I've included a "corrected" sketch.

I feared that the 4 sinks were wrong, though we haven't had any problems with them before the remodel. The bathroom that uses "Vanity 1" is next on the remodel list and those sinks are going to be removed. Assuming that only "Vanity 2" is on that branch, do I need to add venting to it?

With this revelation, the shower/tub is only about 5' from the stack.

Thanks!