@Gblenn there are multicast vlans, broadcast vlans and Switch Virtual Interfaces SVIs and Multicast VLAN registration. You may need an IGMP querier. And IGMP snooping. And to configure the NAT more completely in the VM. None of that is easy. The full duplex 10gbps part seems wild. You may have to force speed/duplex instead of auto-negotiate for each VM.
Some people recommend a NIC for each different VLAN, and plugging them all into the same switch, presumeably to stabilize autonegotiation.
I am just going to quote this since I have been stocking igmp in traffic shaping: IGMP Querier
An IGMP querier is a multicast router (a router or a Layer 3 switch) that sends query messages to maintain a list of multicast group memberships for each attached network, and a timer for each membership.
No clue where you get the time for an SFP+ module. Some people say try PTP and others say NTP can slow you down by 30ms. Most of the time it seems due to machdep on my Zen processor, which transmits data at 70gbps between each core. Some people have built GPSs for their pfSense.