Refer to this thread for a better way to hide the other keys in a persistent way
To automate the saving, there are many hooks you could use, one is the AfterExitEditMode event of the actual text box. Since it’s a native control, you need to get a reference and define the event manually:
EpiTextBox etb = (EpiTextBox)csm.GetNativeControlReference("46567b2e-6bc0-4967-be35-a0ec6843838f");
etb.AfterExitEditMode += (s, a) => {oTrans.Update();};
Verify the GUID above matches your Key1 textbox EpiGUID property, this is visible in the properties, in customization mode.