Online/Distance Math Teaching
There is very little regulation with regards to online teachers, so you probably wouldn't need to get a certification. 
False! Not all online classes are on BlackBoard or Moodle. There's Khan Academy, Lynda, and a bunch of other spots online that are similar. Your skype teaching experience is also not irrelevant at all. A lot of these courses do "workshop" style classes, which are essentially group skyping. 


A few things about teaching online:


don't expect to be paid a whole lot
if you're looking for something lucrative, it can be way easier to join some sort of tutoring program than to teach traditional classes in an online setting with multiple students
most online teaching is now happening in a pre-recorded video format. Production values seem to keep getting better and better. Have you checked out MinutePhysics?
there are so many ways to teach online. If you're looking for a more standard university experience, plenty of universities have online programs. Occasionally these programs get outsourced, so I would look into the companies that they outsource to. The ones that don't outsource, of course, tend to hire in-house, but I feel like they would be open to a new application. Perhaps that's something to consider?


Anyway, I know this is maybe a less clear answer, but hopefully it will give you some ideas with regards to what your options may be.