First off, I believe Sandy Hook is free between Labor Day and Memorial Day. My wife and I go there on those nice spring and fall days and enjoy the lack of yahoo's and bennies.
As far as Gutweed, I have no idea what it is, but we are surrounded by water on three sides.....Raritan Bay on the East, Raritan River on the North, and the South River on the West. So if you're finding this gutweed on Sandy Hook, I'm sure we have it here too. I have kayaks if that would help with collection, and I'm up for an adventure and education. One note, I officiate most every day in the afternoon, so if this happens, it needs to be mornings.
I too am at a loss about how long the UPC will last. I hear people say up to 2 days, and that 14 watts you want to run seems minimal. I'll see if I can find something to plug in with known wattage and see how long it lasts.
And BRS dosing pump tubing.....as much as you want!