Well, first of all- I totally empathize. My daughter did not sleep fully through the night until she was almost 2, and believe it or not, that's totally normal. Looking back there were times when I was so tired and cranky and sleep deprived I wanted to pull my hair out and just leave town, but I am SO thankful that I trusted my daughter to know when she needed me at night and to wait until she was developmentally ready to sleep throught the night without forcing her.
There are several gentle ways that you can encourage your baby to sleep a little "better." Check out the No Cry Sleep Solution by Elizabeth Pantley- a great book. I also want to tell you that your baby is still very young, and still needs you at night, and is NOT trying to manipulate you . Comfort needs are real, and are just as important as physical needs.
Good for you for nursing "on demand." It can be so exhausting but really is what your baby needs. i would definitely NOT follow some of the advice that you were given, specifically to feed him formula before bed and to let him cry it out. Feeding him formula could really backfire on you since it may upset his tummy if he's breastfed. And since he's already sleeping 4 hours for the first stretch (which is great!) it is unlikely that formula would keep him fuller than that anyway. And it;s great that you haven;t left him to "cry it out" at all yet- keep going! Babies are not meant to be left alone anytime, night included, to cry by themselves with no one to comfort them. Before you consider doing something that drastic, please imagine how a baby must experience being left alone to cry themselves to sleep. What a lonely, sad way to go to sleep, wondering where your loving mama is and why she is not coming to help you. Besides, crying it out often causes sleep problems later on because of the negative associations with sleeping and bedtime.
Basically, with my daughter, there was always a reason that she was waking up so much, but sometimes I just didn;t realize it till later. Teething was a HUGE issue for her, plus there were developmental milestones that kept her up, other illnesses, discomforts, and sometimes i trusted that she just needed a little extra love at night. Now she is 2 and 2 months, she sleep through the night almost every night for 10 or 11 hours straight (and yes, in our bed- that is where she sleeps the best) and best of all, she likes going to bed and will ask to go to bed and take naps when she is tired. To me, that is the ultimate proof that I did the right thing by waiting it out,a nd I know I'll do the same with the second. And believe me, it;s not easy- I feel for you so much, but it sounds like you're doing a GREAT job so far- keep it up!!!