I don't know.  We have millions of profiles so we would do it via workflow & sftp with that volume.

Did you try using linecount?  GET https://mc.adobe.io/<ORGANIZATION>/campaign/profileAndServices/profile/email?_lineCount=10

Try https://mc.adobe.io/<organization>/campaign/profileAndServicesExt/

There is no summary level data, only detailed data in the Tracking log.  The article you references is for Adobe Campaign Classic.  That table isn't available for Adobe Campaign Standard which is the version my org is using.

The primary should be the reconciliation.

You will have to do a workflow reading the delivery log.  You can export it to an FTP server for analysis.

You can list as many as you want on a TE.  We send a gift confirmation will all the donations you made.  Here is a screen shot on how that is set up in the email.  

Yes.  You can use an enrichment activity to add that data.

For the query, query profiles you would like to update.  Additional data screen print below.  The Expression is your org id.  For the reconciliation step populate the relations tab, nothing under identification.  Like the screen shot above. For the update activity under identification tab select "di...

Your right I skip a step.  Try this: Reconcile to the organization under the relations tab where you will use the additional field as Source and the destination as @name (note the ID in screenshot is orgUnitlink).  Under the Update activity tab Field to Update use Source to orgUnitlink and designati...