That Broadcom chipset is well-known around here. It can work with either b43 or broadcom-wl. You said that you already installed broadcom-wl (aka kmod-wl, aka wl, aka Broadcom 802.11 STA Linux driver). So you can try troubleshooting that, or you can un-blacklist b43 and try installing the firmware for it. I recommend the latter. Here's why... The BCM4312 often works very well with b43 once the appropriate firmware for it is installed. And if that happens for you, then you would be free and independent of drivers in repos that are subject to frequent updates to keep up with new kernels (e.g., broadcom-wl). It's up to you, of course.
If you want to try b43, then...
Undo the blacklisting that you did for b43 (important for this to work). Then reboot and check the output of this terminal command to see if b43 is being loaded...
If b43 is not
listed there, then you also may need to yum remove kmod-wl
. You can easily re-install it if this goes nowhere.
If b43 is
listed there, then open a terminal and run these commands to install the firmware for b43 (copy and paste them directly into your terminal)...
tar xjf broadcom-wl-22.214.171.124.tar.bz2
b43-fwcutter -w /lib/firmware wl_apsta_mimo.o
Don't be afraid. The only things those do are 1) download a proprietary Broadcom driver file, 2) untar it, 3) extract the firmware files from it, and 4) copy them to the folder /lib/firmware/b43. Nothing more. Later, if this idea is a bust, you can undo all of this by simply deleting the /lib/firmware/b43 subfolder.
Anyway, if all of that completed without problems, then reboot and check NetworkManager for available networks and try to connect.
If you decided to troubleshoot broadcom-wl, then...
Open a terminal and start with these queries to identify the currently running kernel and what you installed for it from RPM Fusion, and to confirm that the wl module is being loaded...
rpm -qa | grep -e kernel -e broadcom-wl -e kmod-wl | sort
lsmod | grep wl
Return here and post all of that stuff.