The first is: does this prompt me to think in a way I did not before? If so, it is not evidence, but it allows you to better way the evidence by providing you with more possibilities.

I think that this would only be true if it prompts you to think in a new and random way. Fiction which prompts you to think in a new but non-random way (that is, all fiction) could very well make it worse. It could very well be that the author selectively prompts you to think only in cases where you got it right without doing the thinking. If so, then this will reduce your chance of getting it right.

For a concrete example, consider a piece of homeopathic fiction which "prompts you to think" about how homeopathy could work. It provides a plausible-sounding explanation, which some people haven't heard of before. That plausible-sounding explanation either is rejected, in which case it has no effect on updating, or accepted, making the reader update in the direction of homeopathy. Since the fiction is written by a homeopath, it wouldn't contain an equally plausible sounding (and perhaps closer to reality) explanation of what's wrong with homeopathy, so it only leads people to update in the wrong direction.

Furthermore, homeopathy is probably more important to homeopaths than it is to non-homeopaths. So not only does reading homeopathic fiction lead you to update in the wrong direction, reading a random selection of fiction does too--the homeopath fiction writers put in stuff that selectively makes you think in the wrong direction, and the non-homeopaths, who don't think homeopathy is important, don't write about it at all and don't make you update in the right direction.