IBU perception can vary a lot but what you're estimating is about half the IBU making this IPA more like a Pale Ale.
If everything was "the same" for this brew. I'd say you had old hops.
When repeating recipes it's important to record Alpha Acid % of your hops, so they can be adjusted in future batches.
Also the age of the hops has a big effect too. There ...
Your finishing gravity always that high? Seems a bit high given the OG and the residual sugars could affect perceived bitterness.
If the beer is finished, there is no way to add real bitterness. You could dry-hop with a couple OZ of Citra & Amarillo but it will only add aroma.
It's difficult to remove acidity from wine without affecting the flavour. You can add salts (calcium carbonate, potassium bicarbonate) to remove some acidity but this is considered a "last resort" solution.
This PDF claims that honey contains malic acid, though it doesn't give a breakdown. It does, however, indicate that gluconic acid is the primary organic ...
Nice brew system Gratz
I have no doubt you're reaching good hot break temperatures. Since your system is electrical heat with temp control with a vented hood.
Water to Grain Ratio
If I had to guess I'd say your mash water grain ratio was really thick less than 1.25 quarts per pound. A thick mash will extract more proteins making it more cloudy. The flaked ...
The biggest consequence of what you did is to add an extra liter of water. Your finished beer will be slightly lighter. For example, if it was to be 4.5% Alcohol by Volume, it might be 4.1-4.2% ABV instead. You probably won't notice the difference.
Hose barbs in that size range seem to usually have a 1/16th inch wall thickness, so the bore would be 0.125" smaller than the corresponding hose. In other words, to get a minimum 1/2" ID in a hose barb, you'll need a 5/8" barb, and change your hoses to 5/8 as well.
To answer the question above, try a hydraulic supply shop, Grainger, truck repair, etc. ...
It's not ideal, but it's probably not a huge problem, either. It's highly unlikely to ruin your brew.
It's most likely happening because the wine in the carboy is cooling, thus reducing pressure inside the carboy, literally sucking the liquid from the airlock like a straw. Did you put the liquid into the carboy hot or warm? What's the ambient temperature ...
I made the exact same stuff last summer. That stuff is LETHAL! lol I got terribly drunk. What you have made is referred to as Country Champagne or Country Sparkling Wine, the sediment is Yeast which made the fizz and alcohol.
You have three options in my opinion
Cold Crashing your bottles and store upright and undisturbed till March. Transfer them gently ...