It's truly amazing how much time and Silicon they put into lighting 3 LEDs! It looks as though they gave a fresh grad a pencil, paper and a databook and no goals (other than to design in as many LT parts as possible! At first glimpse I assumed that all those transistors were a current boosting output buffer, but wtf? more LED related curcuitry.
My advice to the OP would be to throw it in the bin and concentrate on the basics:
1. 10V reference. Off the shelf IC, LT1236, AD587, REF102 etc. All will drive the Dekapot directly. Pay attention to temperature stability, noise reduction, fine trim - minimizing trim range on the pot - something that they forgot to do in that circuit in their LED frenzy.
2. An accurate output buffer. Look through the various voltage reference threads for recommended opamps, DC accuracy, noise etc. Also check output current limit and short circuit protection. Expend 99% of your effort in this section.
3. Power supply. Do you really need battery operation? Does your output buffer need a (small) negative rail to achieve true 0V output (probably).
This Metrology section will give you loads of interesting ideas and information if you browse the voltage reference threads.