In the office/work setting, you can only get people to do stuff if you are the boss or a person of 'authority'. If you try to take it upon yourself to fix and solve problems, your co-workers will look down on you because you'll make them look like they aren't working as hard. Most people just do what they're supposed to do to collect a paycheck and get by. If you want to do something great that has an impact, you have to find others who have the same heart. It's likely you won't find someone like that at the office.
When you partner with somebody, you have to first see if they are in it for the money or are they in it to change the world. Most will be in it for the money. It sucks, but the truth is there aren't very many passionate people out there who want to change the world. So don't try to motivate people with money because the ones you need on board in the long-term are those who have passion.
Are you a developer? I am a UI designer so if you want to collaborate on one of your ideas I'd be open to that.
One of the most important (if not the most important) thing for the success of a start-up is the relationship between co-founders. Forget about the product. It doesn't matter how amazing it is. If the co-founders can't get along, the product is DEAD.
When you lose a founder, you lose the motivation and confidence to continue, you lose part of your vision, and the other half of the "brain" in your startup. The key to a successful startup is to first have a strong relationship and chemistry between the co-founders. Second, is to have a good product.
You say you own 20% right? Do you have this down on paper somewhere signed by all parties?
If no, you get nothing. If you do, then you have a case.
Simple.