I have a lot of wisteria, it's my favourite plant. I find mine stays plenty bushy planted vertically, but if you find that yours is getting "leggy" you can let it float on top of the water for a week or so. It will start growing roots down from the stem and the leaves will start orienting themselves upward along the stem. Then you can plant the stem horizontally and you'll get growth out of the whole length of the stem.
I'm no expert but if you have .1 of ammonia and 0 nitrate AND nitrite it sounds like your tank is just starting the cycle. Has it already been established for a while or is this a new setup? Usually a cycled tank would have 0 ammonia, 0 nitrites but would have some nitrates (the exact amount that's normal escapes me at the moment, I'm sure someone else more knowledgeable could give better info
)
Forgive me if you know all this already, just not sure whether it was a new tank or not.
Good luck battling the tannins - I gave it up after 4 months of water changes and twice a week carbon changes and a tank that still looked like someone poured a lot of tea in it. I replaced my real wood with some really realistic looking fake stuff. Tannins are healthy and all but I like to be able to see my fish
I'm going to soak my wood in a bucket all summer and see if I can get it cured eventually and then put it back in.