Use mobile internet alongside Bluetooth PAN

I've made a website on a raspberry pi that I need accessible from a couple of meters away. At first I set up a Wi-Fi hotspot on the pi, but the problem was that I could not in any way get android to use that Wi-Fi for just the local network. It will always use Wi-Fi for all traffic, which means internet traffic reaches a dead end, even when I still have a mobile data connection.

So I thought I'd give bluetooth a shot. Right now I've set up a bluetooth PAN which works great, except I'm facing the exact same issue as with Wi-Fi. It seems android will also pick the bluetooth PAN over everything else.

Is there any way that I can realise what I want? (I'm running a galaxy s5 with Android 5.0 lollipop)