FYI: When an infopath form has fields that get submitted to a sharepoint list/library to appear in a column then that is called 'promoting' fields. The fields are 'promoted' from the form to the library. Maybe you've done this before. As a side note: you can use a workflow and the action 'get inner xml' to take values from fields within your form and use them as variables in your workflow. Once they are available as variables in the workflow you can then have that workflow place them into columns in the Sharepoint list/library. I recommend this and never use the promotion method as it can complicate things when you later change the form/library/workflow. This 'get inner xml' stuff is well worth looking into.
Your issue: the status isn't updating because the 'Populate Status' workflow isn't triggered. I think are three options.
1. Have the Change Request approval workflow updates the 'approval status' field everytime the approval status changes.
2. Have the Change Request approval workflow update any part of the form record as this will consitute a change and thus trigger the Populate Status workflow.
3. Have the Change Request approval workflow 'start another workflow' namely the Populate Status workflow.
This problems you're having are all about what can trigger what to happen. This is a difficult area. SharePoint workflows aren't great at monitoring progress. i.e. its hard to have one workflow running waiting for some value to change. Its better in my experience to have workflows that initiate when an form/item is changed that then assess the item (looking at fields like status) and triggering actions according to the situation.
Secondary workflows are a powerful tool in this area: http://office.microsoft.com/en-gb/sharepoint-designer-help/create-a-secondary-workflow-HA010237656.aspx
I hope this helps and that I've understood you.