NO!!!! Please tell me that you're not trying a case which is this important based solely on repressed memory voodoo.
Don't get me wrong. There's a whole lot of smoke here and I'm (sadly) pretty convinced that there is fire.
But - OMG - you couldn't get a better witness than one who "blamed [the defrocked priest] . . . for his failure to realize his dream of playing major league baseball" and claimed the ex-priest took him from Sunday morning catechism and abused him in (among other places) the church pews. Now, I don't know this particular church's schedule but every church I've been to has catechism after early mass and before a later mass - activities in the pews would be found by lay members leaving late or arriving early.
There were other complaining witnesses. The only reason I can think of for not using them instead of this complaining witness is that they were worse.