As far as #1 goes, welcome to binary package management.
Linux applications all like to share. The side effect being, when you install the latest package, it wants the latest shared libraries. In order to update those shared libraries, it has to update all the packages that also use those shared libraries.
This is perfectly normal and ok. Most people want the latest version of all the packages anyway.
As far as #2 goes, it's there. http://packages.sabayon.org/show/broadc ... 5,standard
Should be as simple as 'equo install broadcom-sta' to install the package.
Just a quick heads up though, before you install a whole bunch of packages, I suggest updating the package management system first.
'equo install equo --relaxed' should do the trick.