The shadows are blocked because you are underexposing the film. Tri-X is an ISO 400 film and that doesn't change much, if at all with development changes. Shooting at an EI of 2500 is about a 2-1/2 stop underexposure. Using more exposure will solve the blocked shadow issue. Adjust EI downward toward 400 as needed until you get the detail you want in the shadows.
To reduce contrast, reduce development. Time is normally the easiest variable to adjust. Temp changes work fine to. Agitaion is the least effective method.
Believe it or not it's that simple.