Your list sounds good to me. I'd add the otos first because otherwise the puff is going to think the tank is all his!
As for food: DPs are known to be sometime picky. Frozen bloodworms are usualy a winner and as I understand it are better food nutrition wise than freeze dry. It's really easy to feed them frowzen bloodworms. I feed mine with tweezers and they grab it from there! They are such glutons!! As for snails, you could get yourself a small 1G tank to raise them, they don't need much really! (There are threads about raising snails in this forum). Mine totaly love snails!! But the rule of feeding them snails as big as their eyes doesn't work because... well... we are talking DWARF puffer, so the size of a DP eye would be a really tiny snail with no meat on him!!! I give them snails about the size of their whole head and they can easily go for a bit bigger. As for the number of snails a week.. what I do is they have one snail meal a week so I add snails until their belly tells me they ate enough.
You can also feed them mussels and shrimp and scallop. When I buy such food for myself, I cook one in just water for the puff and then cut it in tiny pieces. 2 of the 3 really love it, but my little female eats only bloodworms ans snails.
Be warned that at first they might not eat what you offer. That's because they don't know it's food! Keep offering bloodworms everyday until they eat it. Once they realise it's food, they'll come to you all the time and it's easier to untroduce the other food. Don't worry if it takes 4-5 days, they can take it and sometimes you need to wait for them to be very hungry to gather the courage to try your food! Once they know it's good stuff, you won't have problems anymore! One of mine is like a dog now, he'll eat anything I put on a tweezer!! The other 2 are more picky!
Good luck and have fun!
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