In addition to the other experiences here...
no...a baby will NOT sleep through the night, always.
And, even a teenager has sleep pattern changes, too. Sleep is not static in babies, much less older children or adults.
It will ALWAYS change... per their development, per their phases, per their ailments, per their teething, per the stages of 'night terrors', per growth spurts, per cognitive changes, etc. All normal developmental stuff. It's all about 'growing pains' for the baby/child AND the parent.
My son, is 2.5 years old. Only NOW, have I noticed that he is sleeping through the night, more often. My daughter, also did not sleep through the night until about that age.
BUT, for a baby...if he is waking, it is for a reason. Even if it is due to 'separation anxiety.' One thing you can do, is feed him on demand...perhaps he is growing... and when they are going through a growth-spurt they NEED extra feedings, they need the extra calories, and because they are getting bigger and their intake naturally increases too. A hungry baby will not sleep, well.
But every baby is different.
To me... what matters is the "expectation" the Parent has upon the baby. For example, if one expects a baby to 'act' and 'be' older than they are... both child and Parent will be sorely disappointed & frustrated all the time, because the child is NOT ready to do certain things nor understand things. Your baby is only 8 months old and is behaving normally, actually. Crying it out does not work, for him. You tried. So, just go with what your baby needs. Otherwise, it may just be too frustrating. I know, you are a single parent....and it is hard enough... but, perhaps your baby just needs you. Have you tried co-sleeping? I know that it is not for everyone... but if done only at night...perhaps this would allow you to get more sleep? Or as Deanna Leigh said... going in at short intervals to pat or console the baby.... works for some.
No matter what, its all about the "expectations" we put upon a child/baby, and the baby's own personality. Both my kids are so different in terms of sleeping. What I did for one child won't necessarily work for my other child, and visa versa. So, I had to learn that. I learned to just really cue into my child, and 'learning' what will work for them, versus what will work for me.
Or, perhaps if you can... do you have a close friend or Grandparent near you? Maybe sometimes they can come over and help with baby so you can get some needed and deserved rest at night?
Also, from what you said "if I'm not there then he freaks out.." It seems that he is indeed going through "separation anxiety." Per our Pediatrician... she said that from about 6 months old a baby starts to experience this... and YES even at night when they should be sleeping. AND they will wake and look for you or not want to be away from you. But as hard as this may be, it is a NORMAL developmental phase.
YOu could also try and introduce a 'lovey' to your son...something that he can cuddle and feel cozy with. From about 6 months old, this is what my son did... he just started to LOVE his stuffed cow... and still sleeps with it to this day. Or try "white noise"? When my son naps, I turn a fan on low, before i leave the room. He likes it and will even tell me to turn it on if I forget. Try to see what will help "soothe" him.
Or maybe your son is teething? They do get irritable at night and wake more because of it.
It is not easy... and I really feel for you. I have a Hubby but I still get so tired from waking at night for my 2 kids on certain nights because I do the night time duty too.
I don't have a conclusive answer... just some ideas.
All the best,
Susan