OP yes, there is certainly a light at the end of the tunnel and I felt very much like you do, about 8 years ago. It felt endless.
the thing is toddlers are exhausting and once they get a bit older they really do calm down a LOT. until ds1 was about 4 and went to school he was a wild thing but then he really did settle, he slept all night, went to school all day, it was great. I was human again! Even though I had ds2 by then and he was quite a calm little boy, which helped.
I actually felt a lot of the stress came from resenting ds's father, for leaving, for putting me/us through it, I was so angry. And he buggered off completely and wouldn't even answer calls, so we totally lost him.
But then after a while I realised that I could either spend my time being angry and wishing I wasn't doing it, or I could accept it and make t he best of it and this was a revelation - once I stopped blaming someone else, I accepted it as my job, and that meant I had a right to be a good parent, I had a job to do, and blow me I was going to be good at it.
So I stopped relying so much on my family and I took on my own children and things got so much better. It was all in the attitude.
And after a year or two of that I was grateful to be on my own. I was Ok, the kids were Ok and we didn't have to think about some idiot who hadn't the guts to hang around and help. I was glad he wasn't there.
I still feel that a lot of single parents cope better than they were allowed to when their childs father was around. Does that make sense to anyone? you can really be yourself and do it your way and not be restricted by conflict or having to meet someone else's standards or expectations - let the unimportant stuff go, and focus on what yOU think and feel is really important and be proud of what you are doing.
Good luck and hang on in there as yes things definitely do get much easier.