IDS handles jobs on a first come first serve base, even when you have multiple instances. To be able to control the queueing and monitor status of the jobs I would advise to build your own job/task manager.
Send all jobs through the task manager. The manager registers all incoming jobs and provides them with a status. Displaying the task manager properties will supply you with the information. Offcourse you would have to register all actions of the jobhandling. This means you have to log all actions per job (sent to IDS, returned by IDS, job completed/failed).
Using multiple instances for different jobtypes can make the logging a bit easier because each instance has its own logfile.
IDS does not have a built in loadbalancing mechanisn or queue management sytem.
We use a SQL database to store all jobrequests from different systems and distribute it to a set of InDesign Servers.
I implemented this Workflow a few weeks ago with PowerSWITCH-Software from the company enfocus.com. SOAP Request with PowerSWITCH are produced and transmitted at ID server. Afterwards the response is analysed. With an error the jobs are shifted into a Error-Folder and the user is informed about it. By file balance each server gets the same number of jobs. The status of the servers is always queried by additional SWITCH-Scripts. If the server down, automatically a mail transmitted to the administrator. And still many other functions.
Presently I do not know other solution. With this solution I have the check of the ID server and in the case of error am always informed. An integration of pit stop server for pdf check is possible and very easy.
For this Workflow there is no complete solution from the Company Enfocus. That is a self-solution.