You cant deny the similarities with Mephistopheles and the blood contract however. Keep in mind Faust came before Lovecraft and influenced much of what he created as well. I dont think its a stretch whatsoever to believe From took some inspiration from that source as well.
Sure, but it's more of a shared themes thing than direct influence, imo. A blood contract is as generic as it can get. I don't think anyone was like "woah, a blood contract, Miyazaki sure is a genius". It's just whatever, just fits the whole blood theme, and it's a contract. I'd like to think Miyazaki is a good enough writer to come up with generic stuff on his own.
Also the character doesnt necessarily "seek out" knowledge but through his actions its what he inevitably does, and is required to do to reach out to the great ones.
But this is Lovecraft, this is Cosmic Horror. The protagonist aquires eldritch knowledge either by investigating out of his own will or stumbling upon it, and eldritch knowledge leads to madness. You can't have a lovecraftian cosmic horror game without it.