For S and TX INT yes, they work in couple.
Look at 3GPP to find the exact formula… but otherwise you can simply use the default value of TX INT = 50 with S = …? (isn’t it written somewhere in your docs ? i can check tomorrow for the S value, i forgot 🙂 )
For IMM Asg Reject : yes, it will reduce sd congestio and racch failure etc… Why didn’t you enable it already ? we gave you all details about this feature in past posts…