Then you are essentially among the "single parent" category, even if you don't have custody of your sisters. As you are putting their welfare as your top priority, that's going to make any other priorities in your life (like dating, like finding and maintaining another relationship) very difficult not easy.

Heck, maybe you should try dating other single dads (or dads who have split/shared custody) because maybe they would relate to not having a lot of free time/money for hobbies.

But I'm also afraid at that point (dating other single parents), the relationship you find will be based more on the "battle buddy" system because your actual lives revolve around taking care of your family responsibilities, and the actual relationship will always seem/be secondary to that.

The potential consequence of having such a relationship is that once your sisters grow up and become independent, who will you be? And what kind of relationship will you want at that point when you have more time? Maybe the relationship you found during the hard times won't be the relationship you need or want once you have more time.

And honestly, you don't sound too content with your life, and I think you know it, because you are lacking social interaction and engagement. I'm guessing you used to get that from your volunteering, but now you don't even have that. Now you seem to have only your work interactions. I don't think I've seen you mention hanging out with friends...

You appear to have a finite number of hours per week, on a set schedule that you can use to meet another person. You might be able to date with that time. You might be able to find a friends-with-benefits at that time. And maybe a "battle buddy" relationship.

But it is not going to be easy to find...

You know what, nevermind all that.

You're on reddit. You'll be able to find someone on reddit who will either understand or put up with your other priorities.

Check out one of the "reddit for reddit" (r4r) subreddits, preferably in your local area. Check out /r/OKCupid and message the people in your area. Heck, check out /r/ForeverAlone. There's tons of people online and on reddit who are lonely and wish they had someone for even for a 1-2 days per week relationship.

You don't have to be bouncing off the walls with hobbies and activites. How you present your life (positive connotations, not negative) will do a lot for your profile.

You're going to have to spend some time meeting a few duds that don't click with you before you find one that does.

Don't settle. It's going to be hard, because you're going to want to settle for "good enough," and you're going to have to fight the feeling that you can't ask or expect more because you have so much else going on in your life. That doesn't mean you need Hollywood-rom-com-stereotype of a hero. You're allowed to have some standards (just like everyone else, just not ridiculous standards).

tl;dr: You sound like a decent, hard-working human being. You can find someone. It's not going to be easy. It may take time. But chances are there's someone out there who will understand and accept you in your current situation. They may be in a similar situation themselves.