You need 2 vents.

All the fixtures must be vented in the conventional manner as defined by code and the fixture vent may not be connected to the sewage ejector vent.

In this instance you are creating a totally separate DWV system. Your toilet requires a 3" drain line and under the International Residential Code(IRC) it would require a "Main Vent" which must run undiminished in size from the 3" through the roof thus your fixture vent would need to be 3" and it must run through the roof.
The UPC does not require a "Main Vent" but the combined cross sectional area of all vents must be equal to or greater than the cross sectional area of the main drain. In this case your main drain is 3" and you only have one fixture vent so it must also be a 3" vent and it must run through the roof.

A sewage ejector vessel is required to have a separate dedicated vent to the roof and it may not be connected to any other vents in the structure. Under the IRC the minimum vent size is 1-1/4". Under the Uniform Plumbing Code(UPC) the minimum vent size is 1-1/2".

Most codes no longer permit running any drain or vent lines on the exterior of a structure so you would be required to enclose it in a chase.

You may have a horizontal run however under the IRC if the total developed length exceeds 40' you are required to increase the size by one nominal trade size.

Also keep in mind that although the discharge line from your is only 2" (1-1/2" with a macerator pump) it may not be connected to a branch drain line or a 3" house main drain line. It must be connected to a house main drain line which is 4" or greater.

Hi Lazypup
Thanks for your response.
The macerator I am using is a SaniFlo system which has a 3/4" discharge line which will be connected to the 4" house main drain. Manufacturer recommends a 1-1/2' vent line from the macerator (which is directly connected to the toilet) and then "cutting in" (my laymans term) branch vents from the sink and shower (which are also connected to the macerator and discharge through the same line as the toilet). This "Auxiliary Vent" will not be connected to the main stack but will exit the house independently.
The total length of this auxiliary vent line will be about 30'. Theoretically, will this work?
Honestly, I would leave it to a local licensed plumber, but cannot find one who is familiar with the system (have been trying to find one for over a year).

I would suggest you contact your local code offials and discuss the layout with them. While your manufacturers instructions suggest connecting the fixture vents to the sewage ejector vent both the International Residential Code and Uniform Plumbing Code require a sewage ejector to have a separate vent that may not be interconnected with a fixture vent.

You should also know that code requires a backflow preventer and a manual gate valve on the discharge riser from the pump. The riser is also required to rise to an elevation above the level of the line it will discharge into and it must be connected to the gravity flow line (4" drain) through the side opening of a Wye with the side opening on the top of the pipe. (If you would like an illustration of the installation requirements send me an email..I have one i made for the apprenticeship classes that i can send you).