Your log appears to be 'okay', but your resolution may be a bit high for that computer. I'd recommend lowering the scaled resolution in video settings just a tiny bit more to reduce CPU usage.
However, that may not be the fundamental problem here. The fundamental problem may be the fact that you're using window capture. Window capture on mac is kind of slow, and may not capture efficiently. Screen capture is the easiest and very efficient, though annoying to capture the monitor for some people. Syphon would otherwise be the most ideal, but doesn't always work with minecraft.