To be fair, while MC is a strong vampire, he's newly turned so he might not really control his powers well yet. He would still have all the inhibitions from being a human most of his life.
After all, when he fights the 3 vampires, the way he kills them is by being so bad that they bite him and die due to his blood.
Obviously this is all subjective and the threshold for enjoyment of this will change from one person to the next, so your points are fair.
According to the dev post a few weeks ago, it should be the next ones to advance. Don't know if he'll finish them already or simply advance them and then finish all other quests before closing these two, but those two quests should be next.
There was someone a few months ago that also had that issue, but as far as I know it's not a common one. I'd say it's something in your PC that causes it for some reason. Maybe some hardware/driver doesn't play well with the animations or something. It's very hard to know what can cause that.
It's like FitGirl's repacks. For some people it takes hours for some reason. Even with better PCs. For others it's pretty fast, even with potatoes.
This was answered at least 2 or 3 times in the last few pages. Search is your friend.
This is a timed notification. It will take about 5-10s (yeah, it's a lot) but then it will advance. If you enable the console and change the DEVroll variable to true, you can also just rollback and forward and it will skip it as well.
To be fair, the card and the visits unexpected aren't bugs. I haven't checked the other 2 yet (it's probable that it's locked due to quest variables. It happened with a bunch last update and the dev fixed them for this one), but those at least are simply cards/achievements where the scene was removed from the game.
So rather than just removing the achievement you had in a previous save, they left it there.
It could be argued that they shouldn't have been left there if you can no longer unlock them in a clean run, but they're more like legacy code rather than a bug. Kinda like when games remove a piece of gear from dropping but still let you keep it if you had it from before.