logamatic R 2107 and constant circulation

I have a question about using constant circulation with a logamatic R 2107 on a Buderus Logano G115 with an oil fired Riello. 

I have a room sensor for the system which is on one circuit of 1 3/4" cast iron heating pipes that feed into what I guess are copper convectors. 

I have taken steps to insulate and improve heat efficiency on a 65 year old home. 

I have recently set the room sensor (RMSETBACK) to the lowest setting for minimal setback of 1-2 degrees but it seems like it sets back more than that.  I still want the domestic hot water to shut down overnight but feel as though the constant circulation for heat will use less oil.

Is constant circulation typically more efficient than night set back given the iron pipes, 1 zone, etc.and then having to heat the living space, etc?

Is there a way to maintain constant temp for heat while shutting down hot water production at night.  I haven't figured it out if there is.

Thanks.

Joe

PS. great site, great resource.  without sites like these i'd have less money and less knowhow!