The "Path of the Holy Quest" with Ivarr is not a bug - it's restricted to a definite set of characters who meet alignment and class restrictions.
But the other issues are all valid complaints and / or known bugs. I'm not sure WHY people are still having trouble with Guyven spawning at this point. It was a problem from day 1 with the original release version and it still is a problem even with the v1.03(840) patch and possibly with the v1.04 patch as well. I suspect the issue is somehow tied into the saved games and the globals.xml files and how they are or are not updated when patches are applied.
I don't know whether I would restart or not. On one hand, its a major pain in the butt to do so - that's a lot of stuff to replay. One the other, from all reports there is some deleted content that is being added back in and replaying it might show you things you hadn't seen before. Sounds like a toss-up to me.
Although it is a bit disconcerting that you are getting multiple spawning bugs - THAT would worry me a bit.
For what it's worth I got hit with a game ending bug on my first run through - and I was DEEP into chapter 3. Major league frustration and I had NO choice but to re-start. Color me one unhappy camper! On my current run through I got hit with the Guyven bug as well, and just decided to blow it off. I didn't need the extra xp - and I can always call it in via the console if I decide to. So I am just going to go ahead and play on. Oh and I STILL have patched to version 1.04. I'm going to finish this jaunt with 1.03 and export my character. Then I'll patch finish the very end game and export again.