If a baby is hungry, feed him. Yes, you will have to get up, yes it's tiring. But, remember, they are babies for only a brief moment... one day, they will no longer be. Enjoy this moment, for it will pass all too quickly.
Your baby is only 17 weeks old. This is normal. Some children don't sleep through the night until AFTER 1 or 2 years old.
For the first year of life, a baby's primary source of nutrition is breastmilk/formula. This is how they survive, grow, develop,heal, and develop their brains.
With this in mind, an infant needs to be fed "on demand." This is the best for them. But yes, that means we don't get much sleep. Oh well. I have not had a night's full sleep since my firstborn... that was 5 years ago! We adjust and one day, they will be all grown up.
I would not do the cereal thing. (a baby's digestive system and internal organs are still developing and it's not for THEM that we give them cereal, but for "us" to "make" them sleep. I don't think it's natural at this age). But that's just me. Each baby has their own pattern, and feeding needs. My son was a VORACIOUS feeder too. And he had the same waking pattern as your son. But oh well. As he grew and developed though... his wakings lessened...and now at 20 months old, he only gets up once or none at all, during the night. They do adjust.
Perhaps... your son needs to feed more, and more frequently during the daytime. Try that.
Also, during growth spurts...they feed more and more often. They need this... I would NOT with-hold feedings for a baby, if that is what they need. But that is just me.
Are you breastfeeding or using formula? If breastfeeding, perhaps make sure your have enough flow. If formula, well you can tell how much he drinks by the bottle.
If your baby is growing and developing and gaining weight appropriately, then that is good and keep up his feedings.
I know, it's not easy and it's tiring getting up...but take heart, it WILL pass. But other phases of development and growth spurts and teething and night terrors will arise also. LOL. So read up on those too. :)
Take care and all the best,
~Susan