MacBook Air For Programming and Software Development

I'd get a bigger hard disc whatever it was used for. The main thing is to make sure is that unless you're developing exclusively for Apple devices that the development tools/environments you need are available on the Mac. There's tons of advice on the web and if you haven't done so already I'd do some research on the IDEs that are available for the languages and platforms you're going to be coding for.

Yes, but you need to allow for future added work requirements.

Nobody ever complained of buying too much memory or disk space. That being the case, I suggest a 512GB drive as minimum.

Programming and app development is not especially demanding so 8GB should do; 16GB even better. But ... future needs ... ??? I suspect RAM will not be the problem.