This is a good post.
Last time I was in Cuba, we used our safe. We kept our passports and 50 CUC for our departure tax in the safe and that was it. Nothing was stolen. Our wallets with our money and our camera, being the only other valuables we brought with us, were kept on us at all times.
We left a few CUC everyday for the housekeeping staff and for the most part they took the tips. However, there were 1 or 2 days where the room was cleaned and they didn't take the tip.
One thing I would like to mention, is you should be careful what you pack in your suitcase because the place it might actually be stolen from is the airport. Our suitcase was searched when we arrived in Cuba. There have been incidents where items have been stolen by airport staff, even in your home country.
Your best bet is to not bring anything with you that is not absolutely necessary.
Also, I think we should always remember, that if someone wants to steal from you, they will. You can take all the measures you want, but if they are determined, they will take it.