Sabastian, For low cost I always start with throwing things out. You would be surprised at how much you can get rid. To really do this you need document everything you carry, I'm thinking there is a good bit more you bring in small items, clothes, etc that we are not seeing.
But what can you get rid of first/replace first?
* I'm with Dan on the filter. My water stategy is just like his... CL tabs...they work great and I too only wait 30 minutes.
* Dump the camelback replace it with a 2.5 liter platy. it weighs 1.3 oz.
* Drop the knife, replace it with a swiss army classic which weighs .75 oz
* Again with Dan on the 2 lights issue. a better setup is a petz elite for 0.95 oz with a photon freedom as backup for 0.30 oz.
Beyond this we would need to see all the other "stuff" you are carrying if you want cheap solutions.
If you have money to spend...
* You can go for a lighter pack (again agreeing with Dan), but you might want to see where the system lands from a size perspective. Some otions might be Jam2 or a ULA pack.
* I don't hammock so I can not comment on this one so that leaves shelter/sleeping as is.
* Kitchen is pretty good, I'm assuming you cook in the pot...if so I'd leave it alone. If you only do freeze dried or Freezer Bag Cooking then you can drop some ounces with a homemade alcy stove and heiny pot for cheap.
Again how about all the other packed suff? First aid, camp soap, compass, map, rain gear, hat, gloves, socks, bear bag system, underwear, camp shoes, tooth brush, tooth paste, etc. This is where a lot of stuff can be done for cheap.
One more thing...question your perspective on comfort. I spend the majority of my waking day on the trail. This is where I want comfort so I sacrafice a few things in camp to get it. What I have found is my over all comfort and safety have risen significantly.