First off it's 7=Unplayable, not 7=unplayable.
There is a difference.
I get the data from the catver.ini, as it has a section for games that are added to mame but have broken drivers.
Secondly you are wanting to remove games with missing or corrupt roms from your list, not non-working roms. There is a huge difference.

Here's how you do it...... go to the directory that the rom is in. Locate the rom in question and click on it. Now press delete. Presto, rescan your roms and it's gone from the list!

Seriously I don't do crc checks for roms when generating a list. If I did making a gamelist would be slower than when romcenter reads the mame.dat file upon bootup. (Just as an example, romcenter has nothing to do with dk)
However there is a verify roms option in the fronend.ini. It asks mame if the rom is ok prior to loading the game. If it's not, it will give you a message to let you know that this rom or roms require attention.
It's your responsibility to make sure that your roms are ok. I just let you know if they are there or not. You'll find that almost every fe out there is like this.