Executing DM sequence with Control M

There isn't one, return payloads of the starting call will contain success/failure messages. You have to make sure call-state polling is enabled first, check the section "Call State For Long Running Requests" in the REST Api Guide. Then check the section "Data Management Execute Sequence endpoint", in step 6 it describes the expected behaviour.

This is for the most recent releases, old ones might return as soon as the sequence is initiated. In that case, the only way around is by communicating success or failure from steps inside the job (i.e. an event handler or other rule).