My wife is a producer, and she does quite a bit of independent post production work (including some DVD authoring)...she uses a lot of Adobe products (you're probably familiar with Photoshop and the like), but I know that one that is often used when they get a film festival disc ready is Premiere Elements. It's kind of an industry standard, but it may not be as intuitive as some of the other more DVD authoring specific programs out there...essentially, if you're not familiar within the world of Adobe products, this software is going to take some learning before you're mastering anything, where as other authoring specific software out there may have more user friendly layouts and a less steep learning curve.
I'll be totally honest with you, I wouldn't have the first clue what I'm doing within that software, but she navigates it like she's driving to the grocery store.
Here's a link for you if you want to check it out...(looks like it's on sale now too for $30 off)
Adobe Premiere Elements 12
P.S. - We use nothing BUT Macs in our house, so that should help with your second concern.