Would it be an option to have the other parent live / stay with you for a few months while things get stable, and then move out when the child is old enough to no longer need 60/60/24/7 attention?
Just because there are plenty of single parents out there finding a way to make it work without support, I doubt any of them would recommend it as a first choice, or do it the same way if they had it to do over. And there is no way those kids are getting the best possible care. They're doing their best, but being awake for 72 hours straight with a screaming baby and no relief makes it absolutely impossible for anyone to be at the top of their game.
When you have no choice but to make it work, you make it work. But when you're sitting there contemplating the possibility of single parenthood and you're not even pregnant yet, I doubt many single parents would encourage it. It's nothing against the parents, but one person doing a job that's meant to be done by an entire family is just not what's best for the kids. So why put yourself in that position if it's not necessary?
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker