Insisting is not going to change the fact that we cannot put multiple feeds into a single RSS widget.
Have you tried googling to see if there are any feed services out there that might take multiple feeds and turn them into a single feed or something like that? There are some services like that out there. Some of them have a fee and limit on the number of feeds. I've tried them in the past for clients and found them unreliable, and slow to update. I've also found that some of them produce feeds with errors in them that some feed readers have issues with. That is one of the reasons I'm reluctant to recommend them, but for you... ?
Google "combine multiple feeds" and caveat emptor.