What problem are you having with mouse wheel activities?
I had a script I used on Vista where I could scroll in whatever window my mouse cursor was over, even if that window wasn't active. Windows 8.1 broke that for me. Now I can only scroll in the inactive windows of the *same* program. If I have two PDF's open in Adobe Reader, I can scroll in the inactive one just the same, but I can't scroll in MS Word without activating it.
As for getting admin permissions, try this at the top of your script:
if not A_IsAdmin
Run *RunAs "%A_ScriptFullPath%"
I believe that whenever you start up your computer you'll be prompted by AHK requesting admin permissions. I got annoyed by that and found that a rarely used function could just be put into its own script that I can launch if I need it, so I removed the admin permissions for my script. (But maybe if I run my inactive-window-scrolling script as admin, it might work again.. but I think I tested it and found it didn't.)