Cleaning Up Mess - Subnet/VLAN question (X-POST /r/PFSENSE)

(X-POST on /r/PFSENSE - here )

I am fairly new to pfSense and have some questions.

Anyways here is my issue: someone didn't plan things well and I am trying to cleanup behind them. I am racking an environment and cleaning up a huge mess. Current setup looks like this:

Dedicated Fiber <-> Copper Handoff <-> 5 port switch (eth0)

5 Port Switch (eth1) >> Sonicwall >> Public IP xxx.xxx.xxx.146 / Private 192.168.1.1/24 >> LOCAL LAN

5 Port Switch (eth2) >> Netgear Home Router >> Public IP xxx.xxx.xxx.147 / Private 192.168.1.1/24 >> Forwarding 2 ports to 2 addresses for PBX

5 Port Switch (eth3) >> Linsys e1200 Home Router >> Public IP xxx.xxx.xxx.148 / Private 192.168.3.1/24 >> Forwarding various ports to NVR System

My problem as it appears to me is that the PBX and LAN are on the same private networks. I am waiting to hear back from the phone provider to see if they can push an update to the phones and move them to a different network and my life would be great. From others who have dealt with them I am told that they will want to come out and update every phone manually when I imagine they could push an update and I then just change the private network address. If this isn't an option am I stuck readdressing the entire LAN?

I am currently switching out the Sonicwall & home routers for a Supermicro 5018D-FN8T Xeon D, 16GB DDR4, and 256GB NVMe running pfSense, it has (6) 1GB ethernet & 2 10Gig SFP+ ports. Possibly getting rid of the copper hand off also but that is another issue to be dealt with later. I will also have a Cisco SG300-52 (Layer 3 Managed Switch).

Would it be possible to have 2 identical subnets with different VLAN tags on different interfaces with pfSense?

Place on same subnet/vlan and 1:1NAT or Virtual IP map ports to internal PBX IP?

Readdressing the LAN won't be an option until the following weekend as this is a warehouse/retail and downtime is not an option.