We have recently returned from a trip that included Cuba with a legal entry to that country for Americans. From listening to the info imparted by the Cuban government and hearing Castro in person#to listening to the United States Interest Group (the closest thing to a US Embassy without there being one in Cuba) we learned a lot about life in Cuba.
As for tipping, with salaries ranging from $7-15 a MONTH, no matter the job or the education, tips in cash are the most important thing you can give to the cab driver, waiter, maid, etc.
As for food in Havana, we found good food to be expensive with 20 USD per person (tip not included) for a nice entrée, a beer or bottled water, and a shared dessert. Have lost the card with the restaurant name on it, unfortunately. We also ate at Al Medina near the port, and enjoyed the Moroccan food there.
Food that was terrible, at the Hotel Ingleterra, cost us about 10 USD per person for a sandwich, and none of the three of us came close to even liking what we got for that money. I ordered Tapas and what I got was a 5 layer sandwich made from dried out bread and dry filling.
Some of the group ate lunch at the Nacional Hotel and found it to be very good. I don#t know what they paid for it. I am sure it was in the higher price range, though.
One other place recommended to us was the Paladar, La Guaridia (Paladars are the only type of private enterprise allowed in Cuba).