A couple of thoughts:
If breathing is an issue, pick up a Albuterol inhaler. It's a prescription drug in the USA, but you can get it over the counter in Quito.
It will be marketed in Ecuador as either Salbuterol or Ventolin.
You might also pick up some Zolpidem (5 or 10 mg) if insomnia is an issue. It's sold over the counter in Ecuador.
Zolpidem is marketed as Ambien is the USA.
If you can get some coca leaves to chew once you get to Quito, do so. It's sold most everywhere, but most typically in small neighborhood markets. Coca leaves are truly a miracle cure for altitude symptoms.
Finally, get a prescription for Diamox before you go. It works well, but takes two-three days to kick in.