I have been around macerators on boats and have found them to be a maintenance PITA. If a bottle cap gets into it (no matter how many times you tell people) you end up elbow deep. As stated above, unless you need to pump uphill or run a distance I wouldn't bother.
As long as you have water in the bowl gas shouldn't be able to leak into the coach. It acts like a P trap in plumbing. Also, I put the extra coffee we don't drink down into the black tank. Coffee is the best odor absorber I've seen. Those chemicals don't seem to do much.