What the game needs to do is offer a convincing argument that the tadpole is power you can use without it killing you. It could be based on a lie, but the argument needs to be made.
You really want some old graybearded grandfather named dungeonmaster to lead you dont you? :-/
For one, every character that is talking about how tadpole is dangerous and how you can turn every moment ... is just making asumption, that are btw based on rules that clearly dont aply to yourself, since you would be transformed allready!
For two, you have whole goblin camp full of "true souls" and you know about them, that they all have tadpole ... and since they werent on the ship with you, they once again clearly, have it longer than you. And yet, no problem there!
And finaly, when you will use it, there is litteraly not even single sign of any discomfort, or other health problems nor threatening your life.
Maybe except one evening of sickness, that is miraculously cured til next morning.
And after all, you can even talk with friendly mind flayer, who clearly tells you that your tadpole is different, and that even he have no idea how this will work, since he didnt ever seen anything simmilar ... who else could give you relevant information, if not their own kind?