I've tried this game a few times before but never got around to beating it. I decided to give it a fresh start once again but I wanted to get something cleared up first. Is it true that once you go into the lake (I believe?) that it's impossible to get any more of the collectibles in the starting camp area? I would like to get as many ranks as possible early on because I didn't take them all that seriously the last few times I played. Thanks!

You can still go back to the camp area after going into the lake. In fact you're able to return to just about any area in the game at any point, right up to the end.

There is a Point of No Return. It's near the end and it makes an autosave at that point. Before that, you can still collect all the collectables.

I've also got one more question but it is unrelated to the first one. How do I bind skills/items to Q/E/Middle Mouse? Thanks!

Hmm, well when I used Voodooman's patch and used a controller all I had to do was open that radial wheel for your inventory & powers and move the selection cursor around and push the button.
So I'm guessing that if you use your mouse to select a power/item by hovering over it and pressing Q, E or middle mouse it will bind it to that button.

Before the START of the Meat Cirus surely - before you fight the brain tank as a disembodied brain no less!