Yep, not a good idea to split strip ailerons that are that narrow. It's far too narrow to get a really significant flap effect from the inboard portions and it'll slightly reduce the aileron response.

The best way around this would be to cut away and install new control surfaces so the new ailerons and flaps could be more along the line of 1.5 inches wide. Then you'll get enough effect to make the work worthwhile. At that point split the flap and aileron spans so they are equal on each side.

For just adding some lift for takeoffs and drag for landings you can drive both flaps with one servo. However if you want to play with coupling the flaps and elevator or play with crow and other options then a full 4 servo wing with all the mixing bells and whistles will be needed.