My impression is that organisations working on S-risks (what you seem to be concerned about) tend to focus on preventing suffering of digital beings/minds (e.g. CLR). If you agree with this focus, technical computer science knowledge of how digital beings might come to "suffer" seems useful; philosophical understanding of what constitutes suffering would probably be useful too. 

Would like to caveat that regardless of the cause you are interested in, almost all organisations would need some expertise in strategy, management, operations, comms etc. If your interests are in such topics, you might do better studying them. Might also want to consider taking advice from 80000 hours!

I'd suggest that you consider computer science and business (with a focus on project management if at all possible). A big focus for you will just be building skills and establishing a good track record of doing impressive things.

Computer science meshes well with your logical, black-and-white thinking. It also tends to allow a wide range of careers/professions (site reliability engineering, database management, front-end design, and others) depending on where you choose to focus. It also provides a lot of flexibility in terms of industry, since organizations of all types need people to design and run various systems related to information.

Business (and especially project management) is (very simplified) "getting things done." This is a skillset that is very useful in a wide range of organizations, regardless of whether they are for-profit or non-profit. If you can see yourself being a good communicator who tends to keep things organized, try it out.

Regardless of the field/area you choose, I recommend trying it out a little before committing to a full degree program. You could take one or two courses at your local university or community college, try a few MOOCs in the subject, do some Sophia.org courses to dip your toe in the subject.

I think that it might be hard to find good^[1] jobs that don't involve "sitting at a computer all day." Most good jobs involve quite a bit of time using a computer.

Obvious caveats:

• These suggestions are off the top of my head, without having done hours of dedicated research.
• You generally shouldn't make major life choices based on the advice of some strangers on the internet who know almost nothing about your life. If you don't have any friends or family who could give you good advice, try finding career counselors or reaching out to new people to seek advice.
• I don't know all the details of who you are, what your preferences, etc. To the extent that you are different than my mental image of you, my advice might be wildly off the mark.
• The world may be somewhat different when you are using your degree professionally than it has been for the past 10 to 15 years.

1. ^{^}

   I'm using "good" in a pretty fuzzy way, but think of it vaguely like some combination of paying enough money, not having to much risk of physical damage to your body, having not too much stress, and having decently good motivation. Colleagues contribute to this, how much control you have over the work you do contribute to this, company culture contributes, etc.