For the email, instead of triggering it per record, what if you made the trigger "At scheduled time" instead? Then you'd make it trigger maybe every day at 9 am or something, and it would have a "Find Record" action to compile all of the tasks that are due the next day, and in your send email action you would insert the data from the "Find Record" action as a grid.
This would give you all of the todos for one due date in one email
The only way I can think to do this with page designer involves the creation of a new table and linking all of your tasks to a single record in that new table
You would then create a view in your "Tasks" table that would only display the tasks that are due tomorrow, and in your page designer, you would set it up to show that single record in the new table, and make it show the linked field to the "Tasks" table. You would then filter it by the view, and this would display all the records in the "Tasks" table with a due date of tomorrow in the Page Designer