"This is a fictional memoir."
noooo no no.
For starters, publishers are a trifle leery these days of "fiction" and "memoir" appearing in the same sentence. Frey-tened you might say.
Second, if it's fiction, and thinly disguised, you can STILL get sued, and LOSE. Anybody can sue about anything, but until last year, we all comforted ourselves that the disclaimer "this is a novel, I made it all up" would protect us.
After the court case in Hall County, Georgia, that changed.
So, no "fictional memoirs" and no "thinly disguised roman a clefs" As a novelist you always got to make stuff up; now you really have to.