based on a true story?

IMO it's easier just to call it fiction.

NO - no hard nor fast rule:
for screenplays - no one cares about it being based on truth or not. and since it's loosely based on your experiences then you have no problem with attaining the rights to sell it.

write what you know is a writer's tool. you're just using that tool. and anyone who uses this tool can apply their experiences to the stories they write.

I would just call it fiction. . . It reminds me of the script I am writing which is loosely based on a short story I already wrote and published. . . it has the same name but the story is completely different. . . can I really put in the credits "loosely based off the story by Weren Cole?" Probably not.

Maybe if you get a query together you can mention that it is loosely based on actual events to your agent or the producer, otherwise I am not sure it really matters. Just write well and tell a good story and get it sold. The other stuff finds its place in the world after that.