Ok, let me say on a sidenote Dawngaurd is incredible!

Back to the topic though, I have become addicted to these ''what can I help with?'' sidequest at the castle. I have performed 5 of them,I just want to know if these quest are radiant or are there a set number?

Radiant

yerp, theres unlimited

Awesome! Thank you guys very much for the info.

They're unlimited, but some have unique rewards. Specifically the one that gives you the two vampire rings, and the one that give you the two vampire amulets. I think some of them make the Chalice's effects longer as well.

this

Don't you eventually get to wipe out the Dawnguard also?

Yes, which to me was stupid. Shouldnt that be part of the main quest?

In a way, yes. but think of it this way.

The Dawnguard was never a concern to the vampires in the past few centuries. this new group of ragtag hunters certainly wouldn't pose a serious enough threat to the most powerful family of vampires in skyrim (maybe even all of tamriel) for them to put their destruction before fulfilling a millennia old prophecy. In fact, Harkon's obsession with this prophecy, along with his goal being finally in reach, probably made him not even notice the Dawnguard reforming. this is why his less busy underlings were charged with stopping those who opposed them. Being as arrogant as most of them are helps to support this theory

^^^ Sums up your purpose in DG

STOP DOING THE QUESTS they can bug with vingalmo i repeat STOP untill patch

yep hit a full stop with the vingalmo bug.
now the only person i get sent to is vingalmo no matter how many times i reload a save.