I believe there is a default length for the Read. If you pass in a number large enough or larger, it will read up to the length you specify. I see no harm in having a very large number.

I am pretty sure that the task needs to completely finish before the next iteration can start. Task manager will not run the same task twice in parallel. The running task will not be stopped just because another iteration is scheduled.

I would not create record mapper unless you want to make sure the data is in correct format. If you already have record maps defined I see no issue using them.

Sometimes the IKO wants to scale down our compute stateful set while the Interoperability productions are processing messages. A compute will shut down before it empties its queues and we do not see in Message Bank all messages that were processed before the shutdown. I wonder if anybody wrote code to prevent accepting more messages (stop incoming services) and process what is in queues including Message Bank operation queue which could be called before the actual shutdown (preStop hook)?

That would be okay in my mind if that were specified somewhere I see it. I was unhappy when I realized my input cube had been cut up differently from the example shown.

I don't think you will lose your routines. You can export them if you want to be double covered.