I haven't read all comments so excuse me if this has been mentioned, but you should hand in resignation now with minimum of notice period. You say that you are

I haven't read all comments so excuse me if this has been mentioned, but you should hand in resignation now with minimum of notice period. You say that you are currently desperately needed now, so your leverage to work-out an equitable legal arrangement with them will never be greater than now. As you said, in 6 months you may not have any leverage. Just my $0.02.