As David already pointed out traveling by boat on your own sounds really dangerous and I would highly advise against it!
Even if the boat can be used offshore and if the conditions are well (calm weather and sea), you are not an experienced sailor, right? Additionally the sea is getting more rough during winter months (that's what the Hellenic/Greek coast guards says on their website).
If the Greek coast guard finds you in the open sea they will probably pick you up to save you from the dangerous situation that you would be in at that moment. But you'd have to meet one of these ships first - and that's not guaranteed!
I understand that you are facing an unbearable situation at the moment, but all in all this is a plan that I definitely wouldn't recommend.
Still I wish you all the best,