-How can I prevent Vms on that switch that I don't want to mirror to from seeing the mirrored traffic?
All VMs on the same port group will see this traffic, but remember that if you don't have a sniffer listening on promiscuous mode on the Guest OS, the traffic not destined to the VMAs will be ignored.
-How can I send that traffic to a collector with a destination IP outside my subnet that requires going over a router?
Unless I'm missing something, you can't since the router will forward only the traffic directly destined to the remote IP.