You're literally at the halfway point. But, if you finished most of the side quests, then, it'll probably be further down.

I'm replaying on Hard and enemies feel like they take the same amount of bullets to die. Which actually isn't that much... It's just that most guns in the game have horrible spread and accuracy.

That's why in my first playthrough, I almost always ran with a Sniper rifle (The starting bolt action one... The auto one was rubbish). Complementary weapons often include the Mac 10 (Only for CQB), grenade launcher (For fun) and flare gun (Even more fun)