>they are all being stretched to their capacity.

1: Anti virus and malware detection don't have a 'capacity' - no idea what you're talking about.

Make it so no one can connect to Tor unless they are certified clean.

2: Whether your an exit relay or not, viruses would not come from Tor. Your relay is just a tunnel for encrypted traffic to pass through, there is simply no way a virus could get onto your machine that way as nothing stops at your machine and if you were to sniff what went through it would all be encrypted.

If you've been on Tor yourself and downloaded things from the onion sites then it's your own fault, same as the regular web. You're blaming the wrong program.