is it possible to use my blueyounder broadband internet connection as a slave modem for my nokia 3650 in any way via bluetooth for internet access?

you need to setup a new Access Point.
Set it up as follows:
Tools - Settings - Connections - Access Points - Options - new Access Point - Use Default Settings
Connection Name - Bluetooth
Data Bearer - GPRS
Access Point Name - bt
User Name - None
Prompt Password - No
Password - **** (none - leave it as it is)
Authentication - Normal
Gateway IP Address - 0.0.0.0
Leave the advance settings as they are.

After your done connect your pnone via Infared or bluetooth first and make sure that mRoute is connected. Then connect using IM+ or webviewer.