Welcome to Kokos!!!!
Right now the water parameters you are showing are definately not good for your fish. Anytime the water is less than quality, the fish are stressed. When they are stressed numerous problems and parasites can take over and really do a number on your fish.
So the first thing you need to address is the water quality issues. A reading of 20 nitrite is toxic. A reading of 200 nitrate is toxic. You must lower the concentrations of nitrite and nitrate immediately. Doing a 10% water change every day or so will not touch these numbers. Immediately do 30-50% water change. Do not change your filter pads or anything. Test the water. If your nitrite is not under 1ppm and your nitrate is not below 40 at least, you need to do another change. Immediately. This changing will dilute the toxins to lower levels.
To have nitrates in your tank, you must have had a decent cycle going. So there must be a reason that your ammonia and nitrite have spiked so much. I am not familiar with the AquaTech filter - but when you changed out the filter pad, is there any media left in the filter that contains the beneficial bacteria? Is is possible that you changed out the best part of tyour cycling bacteria and threw them out? Since you had a cycle going, hopefully you have enough left in gravel, decorations or the filter to rebuild it quickly again - given a little time and care.
My next question is..... are these plecos common plecos? A common pleco is not a good tank companion for goldfish - they can and will kill a goldfish - fraying fins and sucking the slime coat and eating holes in your fish during the night.
Your tank, as you know, is really overloaded. Once you separate out the fish into your new tank and this tank, you are going to be faced with a lot of work to keep both tanks in shape as they are cycling, but with less fish load in each, it will work much more easily. With luck, this tank will cycle back again shortly and you can use it to seed your new tank.
Now - the white bumps may well be ich - or something else. But many things can be greatly improved if not totally cured simply by getting the water parameters under control. I think that unless you see a dramatic increase in the spots, I would not do anything about them at this time. Work really hard to get the water back into shape and see if the spots disappear.
Please post back and keep up updated!