I was recently terminated from a startup without cause, where I was one of several founders owning a decent percentage of stock. We also had an angel investor (incubator) in with us for a small percentage. All of our percentages are fully vested.
I feel totally cheated, but I'd like to hold on to my stock because I believe the startup will be very successful. But, the remaining members have been trying all sorts of games to get my percentage back. I am aware that dilution will happen as new investors come in, and I'm not really concerned about that as long as it's done 'fairly' i.e. everyone is diluted by the same amount.
Sorry to hear of your situation.
I'd be concerned about the company flipping its assets into a newco and wiping the slate clean - difficult with a pre-existing investor, but theoretically possible.