- I think Fen'Harel stored the remnants of his god power in the orb (and then questions: he took it with him to the Fade? Kept it in the crossroads? Hidden somewhere in Ferelden?) after the Great Betrayal and focused on stabilizing the status quo after locking out the old gods/elven pantheon somewhere and raising the veil. I consider the orb as a form of a backup copy, just in case

I think his slumber was actually guarding/observing the Fade and the "real world", given the dalish legends about Fen'Harel still wandering in the Fade and this is also how he acquired his Fade stories he shares about old ruins etc. It is likely he was travelling across Ferelden during all this time, though I tend to think though his slumber took place either in the Fade directly, either in "some place in between" like the crossroads and he returned physically to Ferelden just lately, to help with the Breach
(I just saw new posts on codex entries on DA2 and plan to get a closer look on them asap). Maybe a compromise would be that he was travelling through Ferelden across the Fade, which will fit in into conscious walks in the Fade and again dalish legends about Fen'Harel wandering there.
- I think Solas was able to close/open rifts just like IQ can now and I tend to think he used exactly this power for the Great Betrayal. No wonder he's the one to drag IQ hand to close the 1st rift. I actually believe IQ "stole" unwillingly some of his power and Solas initial treatment of unconscious IQ was also investigating the power he/she acquired. I also think this is one of the reasons why he's concerned in the balcony scene, if the Anchor changed the IQ in some way.
- Funny thing though is that the power IQ has now does not make him/her "Fen'Harel creature", similar one to Mythal's one when you drink from the Well. Maybe the Anchor is not enough, maybe it's a difference between Mythal and Fen'Harel...? No idea. Maybe this is an argument for the theory that IQ+Anchor = new power, unfamiliar to Fen'Harel himself. As for me this is another trait of DA lore going into deifying the protagonists, but maybe this is too much of a speculation at this stage.