How to prevent API Throttling?

How to prevent API Throttling?

I am working in a CREATOR app that will create a pick list for the warehouse floor. 

The basic logic is:
  1. loop through all pending sales orders and pull any line_item that is both in-stock and in-inventory.
  2. Output this as a pick list page
  3. The staff marks each line_item as picked/not-picked (picked_status)
  4. update the records in Inventory 
A few problems exist: 
  1. There may be more than 200 Pending sales orders and Creator has a maximum of 200 records can be processed per request.
    1. I can use the query to get sales orders in batches of 200.
  2. API requests are limited to 50 per minute, per API endpoint, per public IP address.
    1. There will be more than 50 line_items.  I don't know how to get around this
  3. I am currently have the function returning a string with HTML formatted table of the line items and the picked_status selector.   
    1. Is there a size limit for the string?
  4. I want to save the picked_status
    1. but the sales order does not have a way to create a custom filed for a line item. 
    2. and there is no documentation for accessing the pickelists module of Inventory
Any insights are welcome.