Everytime you stomped on your diabolos it makes me wince (1:23 and 1:45). I don't think I'm really qualified to give you any advice, because I have only been diaboloing for about 8 months.
So all I really have to say is that you shouldn't stomp on your diabolos and maybe should start learning some integrals and 3d. It seems you know all of the stock 2d tricks, so maybe you could try making up your own original ones. However, I'm sure there are better people on this forum who have more constructive things to say.