ACT and Physical Pain

I have a few questions about ACT and pain
1. If someone finds they get more and more pain the more exercise they do, how do you decide how much exercise to do. If they do "too much" they can then feel like doing less later and have a cycle of increased and decreased exercise.
2. What about little avoidance behaviors that provide relief like shifting your weight? Should one avoid that avoidance?
3. Is there not a risk that if you do creative hopelessness, the person will get hopeless and commit suicide?
Thanks