Rats & other Qs regarding SP campaign

Hello everybody :)
I just started playing RTW, and I only tried the "prologue" campaign.

1) I found that when my city grows, a large portion of the population happiness was reduced by rats (Slo***, I forgot). I already built the sewer and the public bath. In some newly conquered city, the building construction is actually nearly complete, so there is nothing more I could build. I wonder is there any way to phone the exterminator, eh, I mean to just get rid off them?

2) My game crashes to desktop whenever the "custom battle" and the "quick battle" starts to load. Is there any patch for this, or can I change some settings? The campaign battlefield loads fine.

3) The senate now asks me to obtain the surrender of Gauls. I got my diplomat there, but there is no such option. I guess their city has to be under the "besieged" mode or something?

Thank you very much. :)

1. It's Squalor. It's caused by the growth and size of a city. I heard that you could reduce it by not building a few turns, but I haven't tested that (it's not a too much problem for me yet, and I like to keep building ~:)). Other then that, you can build the mentioned health buildings, but thats it. You just need to find other things that make the population happy (like gladiator games and religion.. nobody complains of a dirty city with nice gladiator games and a place to pray for something better ~;p)
2. No idea here.. trying some settings is always okay... never hurts.
3. The option you want is "become proctorate" (see the diplomacy sticky in this forum by Tamur for extra help on this)