1. Why you use iodine to replace bromine?
2. Although china may not adopt TSM (TEACHING, SUGGESTION AND MOTIVATION) rule, it seems that the rule can analyze your inventive step of your invention over the prior art.
3. If you unfortunately fails to pass the rule, you may consider secondary consideration (such as your invention solving a question for a long term or a successful business based on your invention).
4.In addition, I actually wonder that the scope of the prior art you mentioned is directed to bromine rather than halogen. Basically, a good patent attorney will draft such bad drafting to allow bypassing your the case.
5. You may know selection invention to seek a limited scope.
6. If possible, I suggest reading the examination guide concerning inventive step.