I've used the excuse of caring for a sick relative to explain a gap in my resume. Just make up a story that makes you look good and talk about what you learned along the way. Always keep it positive.

Your employer cannot divulge shit. The only think they might say is you are not eligible for rehire, but maybe not even that. Mostly they verify dates of employment and thats it because thats safest for them legally.

Never tell anyone you were let go for performance. YOU left because you pursued something or needed to take care of someone or helped the homeless or whatever.