Hi, I hope I can reduce your fears with some information.
Ring worm can be spread from cats to humans. It does cause an irregular reddish or pinkish ring which can change shape a bit over time a but always looks like a ring.
It is not more dangerous to have ring worm around the navel.
An anti fungal cream will help. Use it for at least 2 weeks. Fungi can be tenacious and take awhile to go away. Try to expose the area to light and air and keep it dry as much as possible.
About poison ivy: The only thing that spreads poison ivy is the oil from the plant. Once it is washed off with soap and water, you cannot spread it. If poison ivy came in contact with any of your clothes, wash them with detergent and that will get rid of the oil. If your shoes came in contact, wash/scrub them with detergent.
But once the oil is gone, which only takes simple soapy washing, you cannot spread it. However, if you did contact poison ivy and a reaction starts, it may appear to spread a bit, but that is not caused by your spreading it with your hands but rather an immune reaction to where the poison ivy oil had been.
Consider treating the kitty for ring worm too if it appears infected. Use a vet rx rather than an anti fungal designed for humans as I don't know the dose or duration a kitten needs.
I hope this helps. Please don't worry - it will be ok.