welcome to the forum!
so far, i like your modifications. good call on upping the malt.
I like using Munich in a tripel, but i usually only do about a 1/4 pound per 5 gallon batch. I'd be interested in hearing how it turns out with a full pound.
what's the point of the maltodextrin?
Kent and Hallertau will work for a tripel... Saaz is always a good call, as well.
the biggest thing you could do to improve this recipe is take that dry yeast and set it aside for a different batch. a lot of your flavor on a Belgian tripel will come from your yeast. My 2 faves are Wyeast 1214 and 3787. DEFINITELY make a starter. You'll want to give the yeasties as many buddies as possible to eat up all that sugar.
If you want it to ferment dry, try adding the candi sugar 2 days into fermentation. (boil it in a bit of water first) - the yeast won't be quite as overwhelmed by the initial high gravity, and will typically finish at a higher attenuation.
EDITED TO SAY: add your malt extract in the last 10 minutes. otherwise, the malt will darken in the boil and your tripel will look a bit like an amber.