Ha, you're basically me. I wiped on Blood-Starved for ages but finally got him and it felt great, I've killed 5 bosses and he's still the hardest so far. There is a cheese way to kill him, but I wouldn't use that method, you'll regret it.
https://www.youtube.com/watch?v=Je8xuJYMisg
If you want to do it properly I suggest using Fire Paper and some Molotov cocktails, and obviously be well stocked on antidotes and vials. And do you have the shortcut for him? The one where you jump down onto the building and through the gate in the stair case? It cuts the run down to like 2 minutes or less and I didn't find out about it until my last few tries.
As for the performance, man, once again you are me. From the second I took my first step I knew something was very wrong with the game and sure enough it has some of the worst pacing I've ever experienced. Apparently From Software are known for releasing games with performance issues and not fixing them so I doubt they'll fix Bloodborne, I will say after awhile you'll notice it less but that doesn't excuse them.