Id say go for it. You dont get any benefits from taking Rome (other than a nice city obviously) but why wait? Once you get the Marian reforms your army will be obsolete ( wont be able to retrain Hastatii etc) so use them up taking Rome/Italy over the next 6 turns and then replenish your legions with the brand shiny new Marian troop types. Also it increases the challenge of fighting and defeating the Senate army, which should be a highpoint of the game rather than overkill.

And for your first question, I wouldnt encourage the Bruttii to get out of Italy. Easier to beat them when they only have two cities. The AI can break down when you leapfrog their objectives. I took Libyeuam and Syracuse as Julii, before the Scipii did. They sat in their cities for the rest of the game, most likely because holding Libyeum was a condition for invading North Africa.