First of all, when making a video, it would help if you help the camera half way steady. That video, (with the exception of you trying to start the engine) makes me,
finally after getting thru the video, there are some things that can be done.
The throttle cable. There are adjusters on both ends of the cable sheath. One at the throttle on the handle bar, the other on the top of the carburetor. Turning counter clockwise will take some slack out of it. If that isn't enough, search on Google for a video on shortening a throttle cable. I really don't think you will be able to do it, surprise me.
The chain. Either move the chain tensioner, or remove a link or two, or both. Chain slack should be about 1/2" to 3/4".
Starting the engine. You need to attain a greater speed before engaging the clutch. You might want to use a shot of starting fluid/throttle body cleaner, to help start the engine. If its still too hard, add another head gasket (lower the compression)..