After a break will be starting a Roman Campaign, which difficulty lvl should I play?

[Kralizec]

I'm aware of that, but I didn't expect that the Averni would be able to keep those towns.

For various I often go out of my way to prop up my allies. In my experience if you save a faction from extinction by returning key provinces to them, they're still not be competitive with their enemies and will usually lose their newly gained cities in a couple of years.

Giving the Alp cities to the Averni and making peace with the Sweboz would merely have made the Averni their main target, and probably would have lost some of the Gallic cities again that I worked so hard to acquire for them. Because I stayed at war with the Sweboz however I divert some of the forces that would otherwise have been sent against my ally.