Since there can be multiples on one object, you are looking in collections for this information, so first and foremost, familiarize yourself with how to filter on a collection here: https://one.workfront.com/s/document-item?bundleId=the-new-workfront-experience&topicId=Content%2FReports_and_Dashboards%2FReports%2FText_Mode%2Freference-collections-report.html&_LANG=en
If you have not ever gone to the API explorer, please start there: https://one.workfront.com/s/api-explorer . You are on a task report so filter on Task and click on its collections tab to find out more about the collection you are interested in. For us, it's the approver status (I'm guessing -- this is the most intuitive name). So click to open it and then click on its link to find all its fields.
From here on out, it's experimentation. You know you're looking for statuses and IDs. So just try all the combinations until you find one that works for you. Handy tip: You can expose this information in a column in a View to help you determine what is in there (the first link I referenced above will also help you with columns). I find if I just concat everything into a view and filter on a test task, I can see what is being displayed on that task and it will help me compose my filter.
For filtering pending approvals on the logged in user, could you experiment with something like this?
approverStatuses:status=AA
approverStatuses:status_Mod=in
approverStatuses:wildcardUserID=$$USER.ID
and then for filtering the approved or rejected tasks, something along these lines?
approverStatuses:status=AD RJ
approverStatuses:status_Mod=in
(the two statuses are separated by a tab character of course)
You'd have to validate on your own system of course. Our system doesn't use approvals very much so I don't have a lot of variations to run QA/QC on.