This is tricky; here are a few pointers:
the document count is in fulfilment_requests_total, which is a counter - you'll need to take a rate to get the per-second increase
you can only user operators queries if the labels on both sides match - if one set of results includes job and instance, you can't join that to another set which only includes instance;
the app_info metric always has the value of 1. You can add labels from that metric to a set of results by multiplying and using the group_left function.
Need more? Here's the solution.