QCheckBox trouble + How to refresh a paint window if an other is open over and select

[andreaQt]

My goal is to freeze the state of checkbox when i push the START button and unfreeze it when i push the STOP button, i write this code but it doesn't work (find the line "//SUGGEST WHAT TO DO" and make a brekpoint at about line 186); see the file.
An other question is:
I write an other program that visualize the data that i've sended (with Qpaint->repaint() call), but if this window isn't select the paint window isn't refresh till i select it; what is the best practice to do it? My goal is to refresh the window even it isn't select.
An other question is:
What is the best practice to open an other window and pass to the new window all parameters/class of mainwindow?
Thank you.