I've used a similar setup. iMac instead of MacBook. I've only found lag when using around 30 surfaces in MadMapper.
Can you give us more specs on your MacBook & setup? CPU / RAM / Harddrive Speed / Video file location
Try playing the video do the default surface via QLab, bypassing MadMapper. Does it still lag?
Try playing the video file in quicktime. Does it still lag?
Do you have other applications open? Try going to Applications > Utilities > Activity Monitor to see how much of your system is being used. This will tell you if your MacBook is the bottleneck if its something else.