There's no way to use the hacks with BV installed. The only custom content that will appear in the game is hair, makeup, genetics, clothing and lots. No custom furniture, cars, hacks and etc. When you install BV without the The Sims 2 folder, BV installs without a downloads folder for custom content. When you copy The Sims 2 folder from previous EPs into BV everything is disabled except for the things listed above.
I actually have exactly the same problem in my game. I created a downloads folder myself, but the game doesn't seem to recognize it. Only hair, makeup, genetics and clothes work. Hacks don't at all, neither does furniture. I haven't tried to install custom cars or lots yet. Do I really have to uninstall BV to get the CC to work properly?