Hello Solrock: Well... the Skeezyks is no expert with regard to fetishes. However, I have struggled with my own similar sorts of issues & I've read quite a few posts & replies regarding fetishes over the time I've been here on PC. (This is my second time here, actually.) So, anyway, with that overview as background, what I can offer with regard to your post is, first of all, thoughts are just thoughts... nothing more. (I like to think of intrusive thoughts as being little trolls come to irritate us.)
In an effort to allay my own intrusive thoughts, I employ a Buddhist practice called "compassionate abiding". This involves simply allowing the intrusive thought to come forward... breathing into it... perhaps even smiling to it. Sometimes I will even place my hand over my heart as a sign of lovingkindness & compassion for it. After a few breaths, I then drop the "story line" & simply continue to stay with the underlying emotion... be it fear, anxiety, grief or whatever.
Two things happen when we employ this practice. First, very gradually over time, the strength & frequency of intrusive thoughts wanes. But second, & perhaps more important, is that we learn we can stay with difficult thoughts & emotions without losing our balance... our equanimity. By the way, here is a link to a mental health oriented description of the practice of compassionate abiding:
https://mindsetdoc.wordpress.com/201...e-abiding-101/
That said, no I don't believe you need permission to write the scenarios you write. Every creative writer writes from their personal experience. Friends & family members invariably end up in their stories in one way or another. So, from that perspective, yes, perhaps you are overthinking this a bit, although it is certainly respectful of you to consider how the subjects of your writings might feel about becoming the subject of one of your scenarios. (If you don't already, you could perhaps give the subjects of your writings fictitious names so you know that if anyone else ever happened to read these, the real subjects would not be exposed.)
One of the understandings I have come to, as a result of reading the fetish-related posts & replies I've read here on PC, is that true fetishes can be extremely difficult to get rid of, or "cure". The consensus of opinion seems to be that the way to handle them is simply to find ways to indulge them safely (& legally). The other thing that occurs to me is that it is the anguish... the feelings of guilt & shame people often have regarding their fetishes that is what is of real concern. So my thinking here would be that as long as you're cool with the scenarios you're writing... write on!

Who knows... perhaps this is the start of a career as a creative writer! But if you find you are dogged by guilt over this, then consider seeking the services of a therapist with whom you can explore your feelings. I wish you well...
P.S. I never saw Jurassic Park.