OK, perhaps the documentation isn't as clear as it could be on these things.
First things first, you don't need tk2dCamera to get a game to work in Landscape on iPad like you wanted. You don't even need it for the iPhone4 scenario. A simple quick walkthrough to get you started.
1. Create a (normal) camera, pick an ortho size, and select the correct resolution in the Game window drop down. Make sure the camera is at 0, 0, -10 or something like that.
2. Edit your sprite collection, untick "Use tk2dCamera" in settings. Now, enter Target height = 768, Target Ortho Size = the ortho size you selected above.
3. Commit.
4. Create a sprite from this collection in the scene and set the position to 0,0,0. It should appear at the correct size.
Now if you ran this on iPad3, everything would be the correct sizes, albeit scaled up 2x. So if you worked the other way, and started off with target height = 1536, and ortho size = 13.578, everything would still work fine as long as the sprites in #2 had the same values in there. Hope that makes sense so far, and thats pretty much all there is to how to get correctly sized sprites in 2D Toolkit.
Now that thats out of the way, I'll explain how the tk2dCamera works.
tk2dCamera is meant to solve a totally different problem - in this case, it is ideal for UIs where you'd like to position things by pixel offsets rather than arbitrary units as you would get in the method above. tk2dCamera creates a custom projection matrix, and the origin of the camera (0,0) is at the bottom left of the screen. Each world unit here is 1 pixel, so if you'd like to position a sprite 30,70 pixels in, you simply set the position to 30, 70. (Thats why everything is so big in the viewport)
Unfortunately, there is a bug in the current version of Unity, where the "Camera Preview" box in scene view is wrong and completely ignores the custom projection matrix. As a result of this, what you see in there is wrong. Unity also ignores the custom matrix when drawing the "Camera bounds" box. This is where/how most of the confusion arises.
Anyway, what the tk2dCamera always tries to to, is resize itself correctly to make 1 unit = 1 pixel. This happens on any platform, so if you ran the game at 960x640, you'll see that the sprites are still pixel perfect. So if your game window is really small, you'll end up with hideous huge sprites. If you're targetting a particular resolution, your best bet is to click "Force resolution in Editor", and type that resolution in. This will override the logic so it assumes you know what you're doing and displays the sprites as though they would appear in that resolution, regardless of the size of the game window. 1 world unit is still 1 pixel on the target, but may not be 1 pixel in the game view if its stretched / squished.
Hope that makes sense so far, if you have any further questions, dont hesitate to ask.
Cheers,
unikron