Fermented kimchi with salt and cayenne pepper (even korean cayenne pepper) should be safe as long as the spices carries out their effects keeping mold out, ferment it inside a closed box, exchange the creme fraiche in fish/kimchi-sauce to an eggbased one (if tolerated), the eggsauce is harder to make and may fail if you don't mix it constantly while preparing it, better have a blender handy.. oh and keep out the sugar.
Kimchi usually become moldy after five days so the line should be drawn at three days.
If you have leaky gut stay out of the cayenne pepper or other hot spices for that matter, i guess it wouldn't be a good idea to eat kimchi while having a leaky gut.
Those with leaky gut can make cabbage rejuvelac instead (recipes on google), principally it's made after the same basic guidelines as kimchi.
Overconsuming kimchi or cabbage rejuvelac may though make your bowels go bonkers.