Thank you so much for posting the full crash report, that's a massive help! I've just released update 4.35, which should fix this bug.
It's a tricky one with Kindle Unlimited & I completely understand why you wouldn't want my stories connected to your account/appearing in your recommendations, etc! It would probably be a bit of a faff, but it might be possible to create a new Amazon account using a private browsing window and a burner email address. You could then sign up to Kindle Unlimited using a different/virtual credit card.