I think the first part of the crawl is key to the ‘missing parts’ in Ep III I would talk about Anakin and Kenobi being on a very important mission and that he hasn’t seen his true forbidden love Padme in a long time. The crawl in Ep 4 is pretty vague so there’s no need for a lot of depth. Bringing in scenes from ep 1 and 2 will probably feel weird and out of place, like a lot of 3 in 1 movies from the prequels it feels weird to start with the Maul fight and then just 10 years in time after only 5 minutes in the movie. But that’s my personal opinion ofcourse.
As title I always liked ‘The Fallen Jedi’ and if you want to make it a stand alone movie you can name it ‘The Fallen Jedi - A Star Wars Story’