I'd start pushing the nap a little forward (say 1 pm) and see if he does ok with it and hopefully naps later in the afternoon. IF that doesn't do the trick, then try to push bedtime a little earlier (say asleep by 745 tops). I think that some of the night waking part (aside from the habit) is due to overtiredness cause he's awake for long periods with a rather short nap. Although I might be wrong... this tweaking part is up to you cause you know your ds better and know if this can be applied.
Then, I think part of the night waking not solving is that you're adding too much factors and he's getting confused. You said you've successfully weaned out the feedings at night YAY! but offering the water is confusing (it's like: i don't get a sip of milk but i do get one of water, so it's worth waking for it). If he's not thirsty, then you're reinforcing the habit of waking just to get "something" ykwim? Also by trying a mixture of Gradual withdrawal with pd and then switching to wi/wo might be confusing to him too.
By reading your post, I'd say he's more likely to be settled with wi/wo. But you have to be really strict on this, every time he wakes, you go reassure and wo only the first time. He'll get hystericall and cry for you, just walk in and shsh (no drink offered) and wo. Only if he's physically hurting himself or really frantic, you should comfort him again. If he's standing up and crying, lay him down, no eye contact and wo. IF he's standing but not crying, leave him at it. Only wi when he's crying for you (not mantra crying, no talking, no whining-all 3 of them should be managed by him). Talk to him during the day about night time and that mommy needs his rest. Leave a sippy cup with plain water in a place he can reach in the case he wakes thirsty and let him know that: if you're thirsty, you can grab your own sippy of water cause mommy will be sleeping. He'll put up a fight on the fist nights, after all it's been a full 2 years of waking at night, and you'll have to be really strong about it, but if you manage not to give in and offer something (a cuddle, a drink, etc) he'll get the drill that it's just about sleep and will start doing it. Remember after you've wi to stay outside the room and listen carefully what he's doing, how his cries sound and if he seems he's starting to settle. Sometimes wi/wo doesn't work cause moms hurry in their way in.
Some lo's at his age have had success with reward system. As simple as a chart on his door/wall with
stickers (or mommy's drawings) when he did ok at night and
when he didn't. When he reaches 5
in a row you should treat him with something special. You might want to give that a try, although don't expect much, cause he's still young and he might not be interested in the rewards at all.
Good luck and keep us posted on your progress!
