I am keen to understand what the specific issues you are having with the green screen footage. When I tested them, they did appear to key very easily. I am not familiar with Pinnacle, however, I have tested on Sony Vegas Version 8 (which is about 5 years old) and that seems to have no issues keying the clips (using the built in Sony Vegas Chroma Keyer). In Sony Vegas you need to get the balance right between the low and the high threshold, and add a small amount of alpha blur if needed.
Generally speaking, editing programs are best suited to editing are not very good at green screen which is why there are specific programs designed for compositing, but having said that, you should be able to get reasonable results with the footage. The recorded footage has been captured in a 10-bit 4:2:2 colour space which means that there is loads of colour information for the keyer to work with. Most video cameras record at 4:2:0. There were a few lighting issues, due to the mixed light in the room, so we couldn't get a perfectly lit green screen, and the backlight wasn't strong enough.
Below is a quick one-click key in Sony vegas with no colour correction or green de-spilling. In this you can clearly see the straps from Lucy's dress still key nicely.
To make this better you would need to do the following:
1. Shrink the matte slightly to get better edges (this all depends on the tools in your editing program).
2. Colour match foreground/background. Start by adjusting the contrast (this is easier if you temporarily make the whole thing black and white).
3. Next, match the colour tone (warmer or cooler) and saturation.
Optionally, to help sell the effect,, Add a shadow layer. To do this, duplicate the green screen footage and put it between the main lucy layer and the background. Next, alter the perspective so that the second lucy layer is on the table like a shadow would be. Now darken this shadow layer to black, add a heavy blur to it and reduce it's opacity.
I hope this helps.
As for performance issues, then yes, this is Full HD footage which will require more from your computer system. If you are using the MPEG files, then this will put considerably more strain on your processor as it will constantly be trying to decode the video files. If you do down scale to standard definition, I suggest you first transcode the footage using something like MPEG Streamclip or similar, and do not use a lossy codec like DV as this will defeat all the advantages of the green screen footage. Try and transcode it to a lossless edit friendly format that is compatible with your system.