1) "avatar" size is set in the get_imagethumb() function in pp-inc.php; it's 50% of your thumbnail size. You would need to change the * .5 to something smaller to get a less than 50% size.
2) We support three and to add more would require modification of the code.
3) Not without modifying the code.
Please do not PM me for support or sales questions. Thank you for your understanding.