If you read the feed validation page and click on “help” next to the error involving the date you’ll see that it is indeed the localization of the day that’s causing the problem. The only allowed possibilities are Sun, Mon, Tue, Wed, Thu, Fri, Sat.
As for the trademark symbol, you might try using the Unicode markup instead of ™. The Unicode is: ™ (according to https://www.natural-innovations.com/wa/doc-charset.html, although it also lists ™). I supposed it’s possible to modify your original post to change it to the Unicode.
