Went back and looked at previous threads and pictures.
Good helpers you got there !
I would not lower the arch yet. Looks about right to me.
On frozen sap. The ice generally doesn't have much sugar content so set it aside and just boil the concentrated sap from the center of the ice block. (get a long stem sap hydrometer or a sap refractometor to check.
Your not doing anything wrong on filtering. Once the filter stops letting syrup through you might as well dump that syrup back in the pan heat it, rinse the filter and start with hot syrup.
Keep boiling!
Regards,
Chris