I’m not overly familiar with how Zapier works, but your Step 3 can be something like this.
Have a list of rowIDs, a list of formatted dates (if you have a way to store MMDDYYYY or whatever format you want in a basic column, please do so), then format the “today” value in Zapier the same way and apply the JavaScript snippet.
That should get you the session ID. Then go through the same process in the Participants table. Maybe edit the JavaScript snippet a bit so you get a comma-delimited list of user emails this time, finally put that to your email module as who to send the newsletter to.