Not without alot of messing around, I'd just stick with 2.5.

You can go down to literally a usb stick or even micros card if they support it. Esxi works on an SD card with a few config tweaks.

Yes because they're cheap.

Are you going to update the firmware upon every release? Are you going to monitor for vulnerabilities?

TA have automated software that will find it, and mess with it for funsies

Could the Ilo have died? Was it known working before you took over the system? It's rare but any tech can fail.

Do you have activity on the interface?

Don't worry about it, no one wants to hack your plex server xD just don't expose things directly to the internet and you'll be fine.

Ah okay, I'd recommend softether as an option as it doesn't technically NAT changes to put into place. (easier if you can, but can work without it)

1. Router type literally doesn't matter.
2. Windows server can absolutely get dhcp address
3. You can't remote into Nas hardware as they don't have a desktop
4. Play a bit more and explore these technologies in your own home first, or. You'll have a huge headache waiting to happen.

Skip the pi's

Grab a refurb mini pc off of amazon and max out the ram, and install proxmox. Should have a nice little sandbox for under 150.

Proxmox is the best option here

Just use zfs within proxmox, only reason you'd do disk passthrough to vm would be if you're using esxi and want to use zfs still.

No, everyone needs a Colo datacenter's worth of hardware in their moist basement