shower vent

I am working on a remodel of a shower that was originally wet vented. Currently the shower ties into the main 4" sewer line downstream of a toilet, so I would like to add a dedicated dry vent to help prevent any siphoning of the shower p trap from occurring. In the sketch below, is it...

When plumbing two showers, can I connect vents together, running horizontally over a door or window instead of running two roof penetrations? The total separation distance of the drains are ~6ft (but could be reduced slightly) & there's not another vent within 5ft so they have to have one...

Hello, I am remodeling my master bath located on the second story of my two story home and I would like to remove a small wall to expand the total length of my shower from 48 inches to 60 inches. The only problem is that my shower drain vents up through this wall so if I take it down I need to...