I've now played this same scenario as the Romans. I was again able to gain a major victory, but this time it wasn't so easy. It took over eight years and several bloody operations on land and sea to beat the Punic forces. Some observations below.
For the most part, the AI did a good job. It played aggressively and caused many serious defeats on my forces, especially in Sicily. I learned to respect their big army there, led by Hanno the Elder. Some of the consuls are truly bad commanders, and did their best to ruin my plans. (Perhaps the plans weren't always so good either.

) In the end, I was able trap Hanno's army in Lilybaeum and prevent their fleets from evacuating the troops. It was the last remaining Punic city in Sicily, and its fall brought an end to the war. I think the national morale of Carthage went too low after they lost their biggest army along with the whole of Sicily. I didn't need to send invasion fleets to Africa, and I couldn't really afford to do so, because I needed all the men I had in Sicily.
I noticed the AI sent its African commanders, Mago and Hanno II, to Sicily. I think they both suffer some heavy penalties when operating outside Africa, so it wasn't a very smart thing to do. Carthage has enough other commanders without such penalties, and as far as I know, none of their generals got killed in battle, so there shouldn't have been any need to send the wrong guys to Sicily. In 257 BC, the AI declared war on Numidia, but it doesn't seem to have had many troops left in Africa to actually fight that war. Fog of war prevented me from seeing any details, but I noticed some Carthaginian areas were taken by the Numidians - not cities though.
The AI was possibly a little too aggressive with its fleets. I noticed heavy activity everywhere in the Meditarranean even during the worst winter storms, which can't have helped to keep the precious Punic fleets in fighting condition, unless the AI is safe from those weather-related negative effects.
There was even a small invasion of Italy by a relatively small force led by Mago. It was enough to give me the option to elect a dictator. I used his army to drive Mago away from Italy and then sent the extra legions to Sicily.
If the AI hadn't invaded Italy, I would have had a serious lack of fighting power there. Without the extra legions and alae of the dictator's army, I doubt I could have won. This must explain the poor performance of the Roman AI in my previous game as Carthage. Because I didn't attempt an invasion of Italy, the Roman AI simply didn't have enough troops to try and retake Sicily from me.
Anyway, this is already a very fun scenario to play, at least as the Romans against Carthage AI. I hope my comments help you to improve it further.
