I keep my place at 68 every night. Have every place I've lived. Never froze a coil yet. We have customers who keep theirs lower. One guy sets it at 63 inside and has no problem. Another family with a huge house and 5 ton builder Rheem keep it mid 60s.
The system is freezing up at 68 but runs good above 70
Sounds like you may not be moving enough air. I keep mine at 67 all the time, 13-years old, never iced up once. Filters clean, coils are clean and the system is properly charged. No ice, no problem. I'd bet the 70 degree air you're feeding over the evap coil is helping to keep it defrosted. Low charge, slow air. That's all.
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!
Here in the deep south we keep our house at 69F constantly with no freezing or any other issues. Sounds like an airflow issue. I have several doctors clinics that like to keep there offices around 64 - 65. No problem.