It sounds like you need copies of signed contracts before making any big decisions. If your team is pushing forward without you, or involving you less, it would be nice to have the security of a legally binding contract.

Without knowing the details of projects X, Y and Z it's hard to say what to stick with but at this stage in your career, it's not good to burn bridges. If you do exit X, make sure it's on good terms. Who knows, they may need you again in the future to join another project they're working on.

Long story short, you've clearly communicated that there is more work available than you have time to do. Seems like it's just a matter of determining which projects are most likely to yield positive results (financial or personal/general interest) and sticking with those. In the meantime, hold onto that salaried job. Having that solid fallback when you're uncertain about side projects is extremely valuable.