Ignore the steal letter ratings for your players. Those are used in the Basic game while the online games uses the super-advanced rules. I use the following guideline:
4-8/- (18-
16) If the second number in parentheses is 13 or higher I will set the player to steal more. I read this on the boards years ago and always have a steal % of >70%. Also, it has been posted many times that a base stealing setting of "Very Aggressive" leads to many unwanted steals of 3B. Beware.
In your case, the SP's and catchers you will be facing may give you some leeway.
Check out the "Stealing" section:
https://www.baseballthinkfactory.org/bt ... mrules.htm