Questions and thoughts on the Inquisitor

1: My current headcanon is that Keldar Lavellan is chosen to infiltrate the Conclave by Deshanna Istimaethoriel due to his curiosity of other cultures and uses the Valo-Kas merc band to sneak in alongside Taur Adaar and Mikal Cadash (under the assumption that, as with Origins, all possible pcs existed but only the chosen pc is the one who survives the explosion) and actually bumps into Cassandra and her former lover Regalyan D'Marcall as the conclave starts (probably by posing as a laborer carrying something heavy), when both he and Galyan notice the disguised Grey Wardens hauling Divine Justinia off to be sacrificed. They both find it suspicious and give chase, telling Cassandra to get help. Therefore, both are present when Corypheus shows his ugly mug, and Galyan does something heroic to give Keldar a chance to bungle the ritual.

2: Keldar hates hates HATES being elevated above his virtues, and being forced to shmooze with selfish pricks who only want to advance themselves and not do what's best for the people of Thedas. (Specifically Vivienne) Plus he is very put out finding all the pro-andrastian monuments in the Exalted Plains and Emerald Graves, though he tries to be professional about it.

3:Assuming everything goes well in the War of the Wolves, I would hope that Inquisitor Keldar Lavellan is remembered as a unifier and peacekeeper, though his revelations about Elvhen history might not go over very well with his people. He helped establish elvhen presences in the Free Marches, Dales, and the Frostbacks/south of Fereldan, as well as enabled the formation of the Free College of Magi. Ideally he'd forgo repeating the previous Inquisition's mistake (though he joins the rebuilt Seeker Order later) and disband completely once all is finished (The OG Inq didn't actually disband, they just rebranded).

1) My canon (Dalish mage) is a healer and has experience dealing with humans somewhat when the clan goes into villages to trade.  I also believe that she traveled to the Conclave with 3 of her clan mates, a warrior and two rogues - she is the Keeper's first, granddaughter of the previous Keeper (in my head), and useless at fighting - there's no way the Clan sent her alone. 
I headcanon that she posed as a healer (that was supposed to be there) and the warrior posed as her husband - the two of them successfully bluffing their way in the front door.  The two rogues snuck in, either unseen or walked in with a mercenary group.  My Inquisitor got lost and separated from her companions and literally stumbled onto the scene with Coryfish and the Divine.  Sadly her companions didn't survive the blast (she later planted a tree for them in the woods just outside Haven).
I like to think that Flemeth was somehow responsible for her getting separated from the others and interrupting the ritual when she did.  Flemeth made sure that both the Warden and Hawke survived - so it's not unbelievable that she did the same with the Inquisitor.  Haven't figured out the specifics yet though.

2) For mine:
- She is horrible at fighting, especially in the beginning, and HATES that she now has to kill so many (even if it's to protect others/stop Coryfish).  Really though, the first few weeks in the Hinterlands? no fun was had by anyone (especially her, with it being the first time she killed a mortal), and Cassandra was especially not impressed.
- It keeps her from her daughter, at least until she has her brought to Skyhold and even then she's still away from her so much. (My Inquisitor already has a young daughter when the game starts).
- Orlesians and nobles, especially Orlesian nobles.  Enough said.
- She feels isolated as both a mage and a Dalish elf.  Even among her inner circle, of the two other elves - one keeps telling her she's too elfy and the other tells her she's not true elfy enough.  Not to mention the doubts many of Haven's residents had about her innocence.  Eventually she makes good friends among her companions (and a particular Commander), but I imagine it had to be rough at first. 
- Being called the Herald of a religious figure she doesn't even believe in. And so many trying to make her believe / questioning why she doesn't.

Don't get me wrong, she grew into and liked her role as leader (she was trained from a young age to eventually be leader of her clan), and how much she was able to use the role to help others.... but it's probably not a role she wouldn't have chosen if she hadn't been thrown (from the Fade) into it.

3) If what I've heard about JoH, she (a Dalish mage) won't be remembered very accurately. But basically this: Probably won't be remembered as disbanding the Inquisition, but the future powers that be will try to spin it that they removed her from power.  Of course the events of DA4 could change all this...

I thought they were in Haven, just not up at the actual temple/conclave at the time of the explosion. But I could probably do with rereading lore from between the end of DA2 and the beginning of Inquisition, so I could be wrong.

They were busy transporting Varric and Cullen.