Hi,
You need to look into the function GetWtiUserLikes inside wti-like-post-pro.php file.
1. There is a filter wti_like_post_user_profile_link available for which you need to attach a function. In that function you can link the avatar with the profile page.
2. You can see the function get_avatar. The 2nd parameter is for the avatar size so you can put any value which is appropriate for you.
3. It does not seem possible with the existing code as it may break the layout but you can still try modifying the above function.
Thanks