>>333466In short, basically what need to do is set firewall rules to only allow traffic over the VPN tunnel. As an additional precaution, I have qBittorrent set to only transfer data over the VPN tunnel. If you prefer, many popular VPN services have GUI apps containing killswitches which accomplish the same thing.
That said, if you're on your last legs with your ISP, my advice would be to carry on with what you're doing instead of tempting fate.