Darker than normal? What do you mean by that? You have to be patient with Mr.X, and not to freak out when he is close to you. Once you get it down, there is an easy way to dodge his punch and even the long lunge that the zombies take on you. It wouldn't hurt to look to some top ten tips and tricks video, unless you want to finish it fresh. He will always show up in the library (seems to be his favorite spot) but sometimes walking instead of running, and not opening doors so quick will help him not come around. Also, he stays away from item box rooms.
Make sure you get all the add-ons for the Magnum!
There are two lickers that appear by the office and armory room, but they are easily avoidable if you do some door peeking, and if you wanna take them out, the door is your best friend since they do not come through them. You can get plenty of knives so what I do is slice check every zombie I come across. Once they go down, or are already down, you can slice and slice until they're dead which will save you tons of ammo. Look out for Mr.Raccoon statues since you can get an unbreakable knife for finding all of them. Boarding up windows in pivotal, and knowing the layout of the station better will help you from going into areas you do not need to explore anymore saving you from unnecessary encounters and wasting ammo.
I just got to the final form of Birkin with Claire on run B and I super pissed since I cannot kill him. 27 Six Shooter bullets with only 50 mini-gun bullets is not enough, so now I need to load an older save file and see what I can do. Hardcore is really a bitch!