Your back boiler takes the heat out ot your fire and you end up with
a dead fire that you have to sit over to get warm.
At the same time your radiators that are taking the heat from it are
only lukewarm and never really have any serious heat output.
Keep your oil fired system as is for heating the rads if you want real
heat in them.

It would be essential to have your wood burner standing in the room
rather than recessed in a fire place. If its in the fireplace you lose
a lot of the heat while vice versa.