This line got me thinking:
"4. Divide that by the # of posts per page and round up (say 80 posts, 25 posts per page, 80/25 = 3.2 -> Round up to Page 4)"
I did something similar by using the PostThreadPostsAbsolute to get the post value of the current thread and dividing that with the number of posts displayed per page (in my case, it's 10) wrapped in a Math.Ceiling for the round up.
Thanks Trevor for suggesting this. Got me thinking about it in a different way.