If a file could be repaired (when detected) then Repair would have been on of the selectable options along with send to the chest. So you should start with the least harmful option, repair, move to chest and the nuclear option delete. However, for me deletion is never an option, move to chest gives time to investigate and files can be deleted in the future from the chest.
Trojans generally can't be repaired (either by the VRDB or avast virus cleaner), because the entire content of the file is malware, so it is either move to chest or delete, move to the chest being the best option (first do no harm). When a file is in the chest it can't do any harm and you can investigate the infected warning.
The VRDB only protects certain files, .exe, dll and other system files, it doesn't protect data files or all files, it is not a back-up program, so there are going to be many occasions where repair won't be an option.
Only true virus infection can be repaired, e.g. when a virus infects a file it adds a small part to it, provided that file is one that avast's VRDB would monitor and you have run the VRDB, then it may be possible to repair the file to its uninfected state.
However, for the most part so called viruses, trojans (adware/spyware/malware, etc.) can't be repaired because the complete content of the file is malicious.
As far as I'm aware files can't be repaired in the chest, you would have to copy it out to a temporary location and scan it again, the detection process may give repair if it is feasibly possible.
The two that are in the chest that are now shown as No virus (I assume they were previously detected as viruses ?), you can right click on them and select restore.
