Hi. I'm pretty new to the hobby too, but I learned alot with my first tank. I'm sure you will get lots more advice soon, but the first thing I would suggest is a 50% water change.
Until your tank is finished cycling, although you might not have to, be prepared to do that daily .
Dump the strips. They are iffy. API tests are far more reliable and will give you a more definitive reading. Test daily while cycling and keep ammonia and nitrites below .25. Sounds like you're almost there if the nitrates are coming along.
Don't add any more fish until the cycle is complete and has been stable for a while. Every fish contributes to the bioload and you have to give the system time to adjust. So stock very slowly.
With regards the fungus. I haven't had to deal with that yet and have no idea how serious your situation is. BUT if you have a pleco in the tank, you must be very careful with meds. They can be very sensitive. There is always pimafix which is safe, but it's effectiveness debatable to the situation. That is something someone more knowledgeable will hopefully help you out with. I also know nothing about adding meds prior to the cycling being finished.
I don't know if this was helpful, I hope your grandson isn't too devastated. Be patient.