i don't think there is anything you can do - the prosecution is going ahead without you. The CPS probably thinks (and i can understand why) that you are either being coerced into retracting your statement or your anxiety has given you a false recollection of events.
I don't understand how your husband dosen't know what happened, and if your version of events (your second version, not the first) is correct, why didn't he just say that you'd done it to yourself? Even if you actually put your hand to the iron yourself, you were clearly in fear, he had abused you previously and he was threatening you with a hot iron at the time! This is not normal behaviour, and surely deserves to go to court even if he didn't inflict the actual injury? He clearly inflicted injuries (maybe physical, maybe mental) on you previously. It's very usual for abused women to wrongly blame themselves and i would guess this is what the CPS thinks is happening. I relly don't think there is any more you can do. I presume he is pleading not guilty/