I am putting a new bathroom in my basement with 3 fixtures: toilet, one piece bathtub/shower unit, and sink.
My drain line to the septic tank is about 4 feet above the basement floor.
So, I am putting in a sump basin in the floor with an sewage ejector pump. I've cut the slab to fit the sump and run lines from the 3 fixtures. I plan to run a 2" drain through the floor from the sink and tub and 4" from the toilet.

I have some questions:
-Can I wet vent the sink and tub into the toilet vent? If so, at what height above the toilet drain can I tie in?
-Can I tie in the vent from the toilet, tub, sink with the ejector pump before going up to the roof?
-I have an existing 2" vent going through the roof now, can I tie my vents to this in the attic?

Thanks in advance for your help.