I know this must be an extremely difficult time for you with all the night time awakenings. It is the most stressful time for parents to wake up for a crying infant. There were times I said to my husband even medical school was easier when you could at least give the children to the next team who had slept all night to take care of the infant who had been up all night. Unfortunately for me and many like me there is no respite and we have to take care of them in the morning after they have been awake the whole night. Most children will sleep through the night by 6-9 months but I must say it is variable.
Every child is unique in sleep requirements and each one has a different pattern.
Children get up many times during the night sometimes they may void, have a dream or may be hungry. The afternoon nap is so variable in children that they may sleep soundly for a whole two hours or they may get up in 15 minutes. I would try to keep the noise to the minimum try to keep the room dark sometimes light coming in through the windows may be enough to awaken them. I really am not sure about the merit of using the rice cereal in the bottle and if that will keep your baby satisfied through the night, give it a try if it works go for it or if you want to call your pediatrician talk to him. It is essential to start a routine with babies as much as possible.