Not telling you what to do, but suggesting a way of thinking about your circumstance:
Mentally take Mr. Wonderful out of the equation for a moment. Consider your feelings about what you call "the truth." If you decide that it is the truth and you want to be part of it, then Mr. Wonderful either has to go or join you in it. He deserves honest answers to his questions: you would fight a blood transfusion for your child, you would not celebrate holidays, etc.
You cannot move forward until you make the first decision - JW or not?