How it is possible (if this is the case) to find all outward-facing IP addresses associated with one organization?

I want to route all my traffic through a VPN (Ipredator).  I plan to use ufw under Ubuntu.

I have e-mailed Ipredator but they have not responded as yet and I understand that their customer service is not the best.

My impression is that IPREDator are served by ViaEuropa Routingregistry (viaeuropa.net).  Their CIDR is 93.182.128.0/18

However, there are IPs in this range which do not resolve to Ipredator.

For example:

1.137.182.93.in-addr.arpa domain name pointer anon-137-1.relakks.com

Is there a professional way of removing such IPs or would it just be easier to just use 93.182.128.0-93.182.191.255 (based on 93.182.128.0/18) as the only IP addresses to which I am permitted to connect?

I guess another way to ask this question is: what are the tools you would use to define the specific IP addresses to target?

Thanks!