Reason one is a possibility, but seems unlikely. Eleazarus went on and on about seeing sorcery without the mark, it was pretty clear that it was the Cish... However a little push to solidify that point might have seemed to be reasonable. Then again, sacrificing even a few Cishaurim seems way out of line with schoolman and Cishaurim philosophies. They value themselves so much.
A sacrifice only a dunyain could possibly extract.
For me, reason 2 doesn't make sense. If moe was able to open the portal from shimeh to get them there, he should be able to open it again, from shimeh, for them to come back through. Its the same, unless its a 1 way opening and you can only enter from where the portal is opened and exit where the portal ends up. We know teleporting works via kellhus, not sure why the cish and/or more would have a less functional method of it.