For the OP... I use a brand of spring water with about the same bicarbonate level as you. I cut my mash water with 20% of distilled water and use some lactic acid to lower the pH.
I agree with the above additions EXCEPT for the chalk, it doesn't dissolve very well in water. This quote is from...
Here's the thing with doing a 1 gallon ferment, it's only 1 gallon of beer. The fermentation dies down when the sugar is eaten up. In 1 gallon that doesn't take very long, especially at the temperature you pitched the yeast. I see this a lot on here with small batch guys wondering why it stops...
I made an all-grain Caribou Slobber using NBs recipe with Windsor once....... ONCE...... I won't use that yeast again. It stayed cloudy as hell after a month in the keg and ended up about 1.018 as someone above stated. You shouldn't have any issues with bottle bombs since that yeast won't eat...
Does it clear up when the beer gets warm? If so, it's chill haze. Did you happen to bump the keg or move it? That can rouse up all the stuff that was sitting at the bottom. Is the keg getting near empty?
Yes, you can boil as much as you want and top off later. I would do at least half of the batch in the boil to prevent scorching and for better hops utilization. You can figure out your boil off rate by boiling a full batch of water for an hour and measuring how much is left at the end. Add that...
If you did a partial boil on either one then I'd suspect stratification of the wort when mixing with water. Depending on where you pulled the sample it could read high or low.
You can serve many beers on a nitrogen tap. Listen to the above advice. If you don't get a stout faucet you're not going to get the same effect. Beer gas is the mixture it is so that you can push 30 psi through a stout faucet yet not over-carbonate your beer. The way you want to do it, you'll...