I agree with Bill that high 60s is way too low. When I activated my Ischia, I aimed for low 80s throughout the process. I used a different method (that I learned when I activated my first starter several years ago).
I fed it 4 times a day for the first 2 days, using smaller amounts (1 tbs of flour plus water at a 50/50 ratio by weight. On day 3, I started to discard 1/4 cup of starter and feed it 2-3 times a day with 1/4 cup flour and water at 50/50 by weight) for the next 3 days. Then I upped the amount of flour to 1/3 cup, and discard/fed it 2-3 times a day for the rest of that first week. It became very well established with that discard/feed cycle. I don't keep more than a cup of starter in the fridge at any time (I just don't use that much).
Hope that helps, and good luck.