Does DT Mgr. that works on a PC also have a similar version for Apple? If so, a version of DTM after 11/09 would have an icon on its home page to enable tethering simply by connecting your BB to your laptop.
If not, there is, I believe, a 3rd party software that is available for both PC and Apple. I almost bought it until I learned it was now available on DTM. My trial version worked fine on PC. Forget the name, but I can find it, if you want.
Cost was $30 or $50, can't recall.
GoogleVoice (domestic call forwarding and cheap intl. calls)
T-Mobile lines on unlimited "family" plan - me, wife. Cost is about $80 a line incl. 5GB/mo. data on each line. We have had no landline in 7 years