How about this to see if it's worth spending any further time on CLAMs:

1. Sync the CLAM client on an internet connected computer which doesn't contain your private keys. This can be done within a VM, or a fresh OS install, or even a remote VPS.

2. Copy, via sneakernet, the client executable and blockchain data to a NON internet connected computer. Start client. Import wallet.dat, or individual private keys.

3. If balance is zero, stop here.