Recording in a small window

[Fireized]

My computer is pretty weird. When I play minecraft in a half size window, I average about 150 fps. When I try to make it full screen, I never get above 30. So anyways I use bandicam for my recordings, and I use Adobe Premiere CS5 to edit my vids. Now, I have bandicam set to record at 720p. But when Import it to Premiere I have to change some settings so the actual minecraft takes up the whole thing, if I don't the outside is black because I don't play with mc covering that area, only half size. Unfortunately when you double the size of a video like that it takes it's toll on the quality, and when I export it and upload it, it only shows in 480p. No way can I record my vids in full screen, not only do I get max fps of 30, but the mouse lag is INSANE. Thank you so much for reading this whole thing, if you have any suggestions please let me know!