Anyone who desires 68 degrees for cooling needs low ambient controls
Raising SC at least 3 degree will take more than a few OZ on a 3.5 T system with long lines. As Beenthere said 68 setting is too low. A 68 set point may have cooler return, although doubtful in an attic, and also cool night time temps can be enough to upset the balance and go from cooling to freezing. One other thing a 2 degree SC would indicate that if the TXV was stuck it would be stuck open which will generally not lead to a frozen coil. A stuck closed TXV will have high SC and give readings like it is low on refrigerant.
Anyone who desires 68 degrees for cooling needs low ambient controls
Ya can’t figure a problem out so ya come on here seeking answers without and data or measurements so that way somebody can actually help you. Then when your asked for and explained why they’re needed ya turn into a know it all and bite at the ones trying to help ya. I just don’t get it because if anybody has been on this site for any period of time ya would notice that every time someone is asking for help everyone has to ask for the information they need,would you call tech support for a problem without data.