Try adding 10 gallons of 5.25% bleach (make sure the bottles are 1 gallon each). Test every few hours and keep the levels of chlorine up (if it drops, keep adding more bleach to maintain the levels... this means it is being consumed as it kills stuff or through loss to UV light). Going a little bit higher won't hurt anything in the short term. I have a pool about the same size as yours and went to 30ppm to kill a big algae growth. Mine is vinyl lined and it suffered no adverse effects from a short course of 30ppm chlorine.
There are a number of problems that can cause red eyes. Low pH, high chlorine, high combined chlorine (which ideally should be 0), and bacterial infections in the water are among them.
To be on the safe side, keep your chlorine level high for 4-5 days or so, then let it slowly drop to normal range. Continue to run the filter as much as possible Don't go swimming again until your chlorine leves are in normal range and pH is acceptable (try to get it between 7.4 and 7.6 if possible, but 7.2-7.8 is ok).
Be ready to keep adding bleach as necessary. Never let it drop under shock levels. I prefer to go a bit higher sometimes so that even if it drops a bit it will still be over the shock level.
As mentioned above, the DPD test (the one with powder) for chlorine is superior in terms of precision and in terms of range of values it can test to the OTO test (the yellow to red color matching one). It also has the added benefit of not being carcinogenic (OTO is a suspected carcinogen... nothing horrible, but if you're like me and like to be extra safe, it's a nice added bonus to the DPD test, which is better anyways).