What to do about this ceiling box?

greetings,

firstly, i hope this is the right place to be posting questions. if not, i'll delete it

Upon replacing a ceiling fan with this one (20 lbs), I learned that the box isn't rated for a fan: images

1. would you go forward with the installation anyway?
2. Can i make this apparatus fan rated by attaching a different box to the mount?
3. If not, how would you go about removing the old mount?

many thanks in advance