Being accredited is ideal. However not essential. What is essential is high quality to educational standards. That's what will be recognised the most, externally and internally.
Multiple choice questions are commonly accepted to be the easiest way to pass a course you haven't studied for.
Skype isn't an option, if you understood security or privacy. It's entirely possible to have this sort of functionality, but without things like sampling your desktop, filingsystem, etc, lent to the site the educational courses are run on. Internet access obviously won't be that limited, or they wouldn't of got this far. Sometimes, learning is best done thorugh the use of video etc, in some cases it may be possible to offer reduce bitrate versions or where sensible textual transcripts. However, as speed is a function of distance over time one could simply just wait longer for the video to download. I can remember dialup quite clearly, and I seemed to cope back then. Another option would be to package the course materials onto some form of media - do people still use optical? - and have it posted to them.
The "best" courses for Asgardians is everything. There should be no facet of knowledge ignored. Astrology is the superstitious belief that the various position of stars in relation to other stars somehow has impact on terrestial events or people. I fear you may of intended Astronomy. I've no idea what the second specified field is supposed to be. There should never be privilige involved with educational opertunities. It is something that should be freely available to all. There is far more advantages. In the initial phases, I would doubt there would be sufficient interest outside of Asgardians. If anything, courses could be offered at a cost to citizens of other nations during our startup phase as a way of making this self sustaining. The problem with that, is until we are recognised as a serious educational provider I predict most to be unwilling to pay for a qualification no-one will recognise.
As for operational costs, Initially they can be kept low by recycling and making effective use of existing resources. This server is likely to be able to support dozens of other sites - the largest issue will be storage of many materials: videos, etc - and as for the content itself, this could be produced by those in our number qualified in the appropriate fields in their spare time. Even with a donation of one hour per week of their time, then over time this will collate.
I had lent thought of attempting to register Asgardia as a charity in my country in order that certain operations can take place tax free. If we are offering educational courses on a non-profit basis then this will assist with conforming to various requirements for. I don't imagine the "for-profit" institutions will feel threatened by us in the slightest - I seriously don't think they would entertain launching any form of assault. There's multiple organisations already offering courses sans cost. But these tend to be of limited quality or use.