First of all remove the settings you made.
sudo rm /etc/modprobe.d/rtl8723be.conf
If you do not have this file, nothing is wrong.
Then install a good driver
sudo add-apt-repository ppa:hanipouspilot/rtlwifi
sudo apt-get update
sudo apt-get install rtlwifi-new-dkms
Reboot and enjoy
If you still have problems, you may need to add an option:
echo "options rtl8723be ant_sel=2" | sudo tee /etc/modprobe.d/rtl8723be.conf
then reboot again.
If you do not have any internet connection, you can download the package using another computer, a phone, etc.
The package is HERE
You will also need DKMS installed. You can find the DKMS package for Ubuntu 16.04 HERE
Copy these two files to the Ubuntu Home folder (~/) and run in terminal
sudo dpkg -i dkms*.deb rtlwifi*.deb
Then reboot.