The things to look at most in your pack (some already mentioned):
1. Invest in a lighter pack. It will make your life easier. If you have a small torso, REI has an Osprey Hornet 46 on closeout for $110 (weighs about 600g). Others can suggest better packs for certain, depending on whether you want to go frameless. By itself, this could amount to a weight savings of about 25% of your total pack weight.
2. Clothing-I know nothing about the conditions you'll be encountering, but I looked up some info on Slovenian weather (in August), and it looks to me like you're going to be dealing with temperatures not lower than 8 C/40 F except up in the mountains. If this is at all correct, you don't need to be carrying about 1 kg of clothing in addition to what you're wearing. Look through and see what you can do without at the lowest temperatures you expect.
3. Electronics-You've got almost 500g of electronics, which has got to be more than you want or need. Jeremy's idea of putting the guidebook on your phone is a great idea and will save you another 340g.
4. I wouldn't depend on rocks for tent stakes, but instead buy aluminum or titanium ones. A set of 4 titanium stakes will definitely be under $15, and will weigh in the range of 24 grams.
5. First aid kit and toiletries–Go though what you really need, and you'll be able to cut out at least 250g.
6. You're right about the bladder- switch it out for plastic gatorade bottles or similar, or spend $20 or so to get Platypus bottles which weigh even less.
All in all, it should be very easy to get this pack weighing less than 5 kg, or even 4 kg if you make some sacrifices.