I dont get it.

[Platinum]

One of the monks in Weynon Priory says that Eronor the shepard is Dagails brother but Eronor is Dunmer and Dagail isn't. wft?
How did that happen? lol
Also the woman in the arena bloodworks seems to be inside the cage where the boar is and the boar seems to be where she is supposed to be! And another thing why does the unicorn follow me? It is not set as my main horse it just follows me everywhere it doesn't even care if I or anyone else draws a weapon or hits it.

[The Khajiits of the nine]

Maybe Dagail and Eronor are only half-siblings, They may have the same dad, but a different mum or maybe Eronor was intended to be a bosmer, because dunmer usually have last names. See: Eronor Dagail Notes on Racial Phylogeny.
As for Ysabel and Porkchop, that may just be a glitch. Can you still talk to Ysabel? Check if some mods maybe changing that.
The Unicorn thing? you sure you haven't made it angry? Have you ever ridden it? Then it WILL be your main horse until you mount another horse, whether you like it or not.
Tha'ts all Can think of at the mo...

[Platinum]

It isn't my main horse. I've mounted Shadowmere after I mounted the Unicorn.
If I fast travel anywhere the Unicorn AND Shadowmere are there when I arrive.
It doesn't care if I hit it or anything.
When I speak to the boar it comes up with the woman's  dialogue.
Also its not Ysabel. Its the yellow team champion.

[The Khajiits of the nine]

Hmmm? That is strange...
Do you want the Unicorn? If not than just kill it, although you can't get rid of it as it's a Quest item for Hicrine's Daedric quest.
As for the Arena problem, that's definately a bug. It shouldn't be too much trouble should it? You just might end up fighting with Yellow team Champ and against Porkchop. I looked on UESP and it said nothing about it. Lemme know how ya get on...

[Platinum]

I killed the Unicorn and got the horn but it respawns. Although if I kill it again there isnt a unicorn horn.