Need suggestions to improve topology (eliminate untagged interface)

[pankaj]

Here is my home network topology:

1. The wire from the utility company comes into a junction box and from there an ethernet cable comes to my desk and gets plugged into the ISP modem which provides the WAN port for the OPNSense device.
2. From my office desk there is another ethernet wire going to the utility junction box, lets call it "Return Wire" for clarity.
3. Each room in our house has a wall socket with a RJ45 cable running to the utility junction box, I've connected all of these wires and the "Return wire" with an unmanged switch.
4. Most rooms do not need the connection and there are only two rooms (living and family) which has multiple devices across multiple VLANs.

My OPNSense device has 6 ports, one is assigned to WAN (port-6) and this is what I did for the 5 LAN ports:

5. Assigned VLANs on port 1-4, these ports do not have any untagged interface.
6. Running an untagged interface on port-5
7. After OPNSense device, I attached an unmanaged switch with 8-ports which connects to the 5 LAN ports of OPNSense
8. The "Return Wire" is connected to the unmanaged switch from #7 so it provides connectivity to every wall socket in the house and creates my home network.
9. In the two rooms with multiple devices, I have added a managed switch which allows isolating devices based on VLANs.

But there are two unmanaged switches in my topology - one right behind the OPNSense device and another right after the first one inside the utility junction box.

Two questions:
1. I really want to get rid of the untagged interface on port-5 but do not want to make the sockets in the room redundant as right now it needs an untagged interface for DHCP to work.
2. The two unmanaged switch behind the OPNSense device must be having a ball with several DHCP broadcasts, is there any way to reduce this clutter?

I am also open to adding more managed switches if the above two objectives can be achieved.
Thanks.