The first observation is that the well was not properly installed, or sampled correctly, or the analysis is incorrect. It is very unusual to have turbidity and COD in a deep well. The presence of these parameters indicates the well may be contaminated with surface water.
In a deep well the iron should be dissolved and the water sample should be perfectly clear when drawn. On standing in contact with the atmosphere, the water should slowly cloud and finally deposit a yellowish to reddish brown precipitate of ferric hydroxide.
The recommended treatment would also depend somewhat on the capacity of the system which you have not stated. I am assuming the water system is small.
I recommended two stage media filtration as posted above. In addition, I would also recommend a water softener after the filtration as the filtration will not remove the hydrogen sulfide in the short retention time provided by a filter. The use of a water softener tends to significantly improve the operation of the RO system (in terms of less frequency of cleaning).
If the turbidity is due to the iron, then go with just the water softener.
You should have a laboratory determine what is causing the COD and quantify the hydrogen sulfide.
As mentioned above, some details are missing from the water anaylsis. Before you spend money to improve the system, have a laboratory do a bench test of the proposed improvements.