Illness/Sickness: Advice on emergency temporary removal of Tiger Salamander Larvae from tank?

So, I swear to god I really did spend hours upon hours researching these guys before getting them. Somehow I managed to miss all the information about cycling the tank prior to adding them. Long story short, I ran out of the strip-type water tests, invested in a liquid test kit, and suddenly my ammonia levels went from "not-too-bad" to "oh-my-god-how-are-they-still-alive." Lesson learned, no more strip tests for me.

So I'm following instructions that I've found on here, moving them to buckets (probably individual rather than together, right?), daily 100% water changes, reduced feeding, until the aquarium reaches safe and stable levels. But I've got a few questions which I didn't find answered here:

How large of a bucket for each Waterdog should I use? Is 5 gallons okay?

Should I oxygenate the buckets with an air pump and airstone the way I did the aquarium, or will they be okay without that?

How much can I safely reduce their feeding to make waste manageable?

Anything else you feel like I should know?

There are also some little white pumps on different parts of Billy Joe that have gotten larger, almost like little pimples or abscesses, though considering the water conditions I'm not surprised. He had them when I got him, I'm hoping that they'll go away as conditions improve.

I hope my little guys will forgive me for putting them through this! I swear Billy looks like he's glaring at me sometimes.

Did you cycle the tank before adding them? If not, that may be the source of your issue. Also, how large is their tank, and how many larvae are in it? I think temporarily a 5 gallon bucket would be fine with the water changes you're going to be doing. You could also just do large daily water changes in the main tank and keep the animals in it. Still depending on how old the larvae are, feeding could possibly be cut to 2 to 3 times a week. I would check the main tank for uneaten food or trapped waste to be a source of ammonia. If the tank has gravel then there is likely stuff trapped in it (but this could be solved with a gravel siphon). Adding some fast growing plants like anacharis or java moss would really help absorb some of the dissolved wastes.

Yeah, that is definitely the issue. I read somewhere to let the filter run for 24 hours before adding them and went with that, only recently reading that that isn't nearly enough time. The ammonia levels are currently way too high to leave them in there. I'll be removing all the gravel from the tank too, until I can find a better substrate.

The tank is 15 gallons, with two larvae.

I think 5 gallon buckets should be fine. Don't fill them to the top, or there is risk of leaping out.

Small update:

The tigers seem to be feeling much better in their temporary homes.

I did a water test on the main tank today. Ammonia is still very high (unsurprisingly), but there was zero nitrite and just a little nitrate. Does this mean anything specific?

I also read in the instructions (it's an API freshwater master test kit) that the tests are appropriate to use for testing freshwater aquariums "to which salt has been added." Should I be adding salt to ensure accuracy? If so, how much? I haven't been able to find that mentioned anywhere on here.