Re: "maximum number of sequence numbers (99) has been exceeded"

This looks a lot like a bug to me, particularly if you look at the FieldDefault PeopleCode on SA_REQUEST_DTL.REQUEST_SEQ_NBR:

  If &SEQNO > 99 Then Error (MsgGet(14600, 217, "The maximum number (999999) has been assigned.")); &SEQNO = 99; End-If; 

The field is 5 digits in length (app designer), the error message suggests that the maximum is 999999 (6 digits) but if the sequence number is > 99 it is reverted to 99. I'd suggest customising that field edit to meet your requirements in this particular instance.