I have a trick you might try that I've seen work with remarkable success...in some dings almost as bad as yours which I never would've dreamed were repairable..and it goes like this...
Use ductape and cardboard to build a dam about the perimeter of the ding about 2-4 inches tall....then keep filling that dammed off area with crushed dry ice....and keep it full for a couple hours...meanwhile?...get a pot of boiling SALT water going...to a violent boil...and then?...as quickly as you can?...whisk the dam and the last of the dry ice away and dowse the frozen metal with the boiling hot salt water.
Thermal shock...and as the frozen contracted metal gets shocked with the ultra hot water it rapidly expands and with no where's else to go?...it just may pop out...and that's how it works..but there's two no gaurentees involved here...
1. It might not work and...
2. If it does work?..you risk a chuck of your paint popping off. (however...I have seen it done successfully where the paint didn't pop off at all.)
One things for certain...it's worth a try...dry ice is what?...$5 a block?
L8R, Bill.