I think that the answer is dependent on the level of technical talent that is already on-board. If you have an engineering focused squad, you can get away with rudimentary understanding. To your description a "non-technical CEO" is just that. Of course, whenever there is a gap in the team, it is generally the CEO's job to wear different types of hats as the weather changes. One of those hats may be a hacker.
You can get away without learning any language if you have a technical co-founder who you trust and can play the CTO role.
However its always good to have a bit of technical edge so that you can express your ideas in a more profound way to the technical team and also can sync yourself with the development challenges.
In case of learning a language completely, I believe you should concentrate on the logics of programming first.
You should start with simply breaking down all functionalities of your system in flow diagrams and trying to understand how everything works.
If you are adamant about getting your hands dirty with a language, my advice would be to go for a easy scripting language. (PHP for instance). If you use Microsoft Excel, you may learn Excel VBA which is a simplified version of visual basic inside excel that lets do a lot of fun stuff with your excel data.
And if you don't mind spending some bucks, there is a good course called programming for non programmers in udemy. Google it.
This is dependent upon the industry your business is involved in.
If you're an exotic lumber import export business, I would say learning html and css would not be a good use of your time. However, if you are in a company that does 90% of business through developing websites and web properties, then taking time to at least learn the framework of html and css would imo be a good use of time.