Sales Rep Setup B2B2C

We provide retirement planning to the employees of institutions...

We have vendors who's products we represent. They have call centers as well as external sales reps and their internal assistants, so we utilize the Vendors tab alot. We'll add new contacts under the Vendor Tab but they don't seem to show up... They do show up as contacts but don't share the address information except for the main phone number of the Vendors entry. I assumed they'd be available in the contacts section of the Main Vendor listing so that I could easily find multiple contacts from within the same company.

We need a system to set up parent business accounts with the Employer points of contact within separate departments. Within each of those departments, I have participants who purchase the products on an annualized basis.
Once I convert a leads or potential, I want that contact to fall within a company department inside the parent/master account? I also want to be able to identify where that annualized revenue originated but seem to be duplicating.

We share information between 15 or so reps but don't want this to go live until we can replicate the desired format.

Thanks in advance for the suggestions

Shinyface