Not to ruin your day but the reason for finnys abnormal strength is because he was used as a lab rat before he started working at the mansion<< I KNOW IT'S SO SAD. And yea, he's definitely Chuck Norris inside!
This is what happens to you after years of gaming. Either that is a muscle which one I don't believe you can get muscles in your fingers however. I could be mistaken or you have some serious medical condition like a tumor.