Mouse (( ))
We had the same trouble with DD. She used to wake every 45 minutes, even when sleeping with us. She started sleeping better when she turned two but that only last 2-3 months and now she wakes through the night again.
I have had countless bits of advice on sleep. The tough answer is that he is just a bad sleeper (as DD is) and you have to adjust your life accordingly. DH and I used to have to make a plan every evening as to who would do what and set a shift so that we both got 4 hours straight sleep - taking it in turns just makes for crap sleep all round. And trying to make a plan at 3am just creates arguments.
We also did controlled crying with DD, not sure if that is feasible with Nemo though? For us it was the only answer in the end, although it was horrible. It did work but it doesn't take much to knock her good sleep - a cold, teething, people visiting, visiting others etc. Everything is an excuse for her to test the boundaries (although Nemo's problems may not be sheer wilfullness!).
I have also heard that protein is the key to getting them sleep but not sure how easily you can address this with his feeding? Also frequent waking is a sign of tiredness - they do one sleep cycle and then wake up because they don't know how to either self settle or they are so wired, they don't fully relax. I used to have to walk DD around for hours to get her to nap properly during the day. We had to sort her having one proper day time nap first, then the nightime sleeping followed that. But you basically need to devote a couple of weeks to doing it.
Obviously bedtime and nap routine important but we have a textbook bedtime routine and it still comes as a surprise to DD every night that she has to go sleep. I normally feel like slapping people that tell me to have a good bedtime routine. As if in 2.5 years of broken sleep, that hasn't occured to me. 
A lot of people have told me to use drugs to break the pattern (for her, not me!) but I haven't dared.
Sleep deprivation is debilitating. I don't think I have felt fully awake since she was about 6 months old.