Having said that, looking back at it now, it is perhaps a good thing. I went on to have much better success elsewhere, while they had success in their business as well. Do I feel bitter? maybe in the past, but now I can't be brothered. He still send emails 2-3 times a year taunting me about his success with different email addresses which I simply send it to my spam folder.
Most importantly, what I learn is that, sometimes things just don't work out. The reasons for falling out could be many and weird. For my case, my 2 other founder friends are people who prefer 'Yes' men who agree with their groupthink all the time. I'm not one of them and hence it is not surprising we have to part (Although it turn out for the case which I'm arguing against and got them angry, I turned out to be correct as time passed)
It is up to you if you want to chase for more compensation. You may wish to consult a lawyer if you deem it's worth it. For me I don't want to waste further time hence I did not.