I agree with the fact u have to get some alliances in order to survive with france. In my first campaign, after 30 turns, i was allied with HRE and Danemark against Milan, Spain and Venice. So even though i had 3 fronts in the south, after having wiped the english out, it was quiet in the north and i had plenty of time to build strong armies and settlements.

I was even excomunicated by the pope once, but i managed to survive mainly because huge armies were marching for the crusade, leaving me in piece for a while.

Make sure as well to build merchants and production buildings in order to get some cash when there is no settlement to sack at hand.

Also, i suggest to make some gifts at the beginning to the factions u intend to "bribe". It is like chess, u have to define a plan of actions for a few turns ahead in order to forsee what the futur alliances will be so u don't fight against the entire world alone.