O dear, problems left and right! So very sorry not to have mentioned that you always unplug a heater if its going to get exposed to air. Its very hard for us to know how detailed to get in our help as many get offended with too much detail. Also, we're all different in the help we give (one of the good things about there being a lot of us!) and I'm not great thinking about tube heaters as I have an inline heater and never have to think about such things! But I should have thought about it for you, so again, apologies!
Now, probably, one of the experts will come along and outline the best approach for your whitespot/ICH problem, right here in the beginner forum, but if not, be sure to post up for help in the "emergencies" section, which is where all the disease queries should start out. The folks over there keep up with the latest, greatest approaches as they change over time. Your whitespot problem may have an impact on how you should proceed, as the introduction of medicines changes what you can do with water changes.
Until you can get medicine in there however, the fact that you've brought both your toxins down near zero is very good for the fish and you can continue to water change to accomplish that (based on feedback from your new kit hopefully) until you receive instruction from the disease folks.
~~waterdrop~~