IPTables and OpenVPN issue

[Hayabusa1989]

Having some real issues with setting rules for OpenVPN with iptables on Ubuntu 18.04. 

Main issue being that the rules I write just don't work. 

all I want is for all traffic over the OpenVPN to be blocked apart from port 3389 (remote desktop port) 

I have done this : 
Where am I going wrong i'm really confused. 

[Lukyp]

are you sure eth0 is the name of your physical adapter? I ask this if you copy pasted the iptables commands from somewhere without editing it