Well, weirdest of all things!
I created another Fresh Install from the ISO usb using the laptop. I figured I was overwriting the older, failed versions. After writing, I pulled the ISO out of the laptop and put the bsd USB in the same slot and rebooted (BTW, since I was going to use dhcp, I plugged the ethernet cable in. In the past I'd done all this on a standalone machine on the premeise that I wasn't going to let the network influence the outcome, seems that this was "my bad!"
I chose fresh install choice so I'd get to the console menus, but, weirdly, I saw a comment that the FreeNAS...db was being renamed to ... Anyways, things progressed and I saw the adapter DOWN, UP, DWN again, and attempts to find the broadcast address, etc.
I finally got to the 14 choices and got a "try http:192.168.1.15" which is the router by mac-address assignment for that piece of hardware. I shutdown and moved the USB to the FreeNAS server. And then began the "patient waiting" to ping 192.168.1.15 from the desktop that I'm writing this from. Got "Host Destination unreachable" for 10 minutes. Just before deciding to go back to the FreeNAS server, for grins if nothing else, I decided to ping 192.168.1.10, the static address I'd been trying to enter in the past, which was also hardware assignable by my router because of the mac-address entry. Lo and behold, I started to get pings!
I've now got the web interface up, so I can finish my installation.
To summarize the key points of success from my point of view.
1) You CAN build the bootable ZFS disk on a computer other than the one it will eventually be installed on.
2) Be sure to do the building on a computer that is active on the local network it will eventually reside on during the Fresh-Install process.
3) The documented process works with the dhcp approach, don't know so well with forcing static assignments at this time.
4) If you manage your dhcp pool using mac addresses, try pings not only at the address you get from the Installation, but also at the IP address you have told the router to use for the hardware the boot stick gets moved to.
Thanks for everyone's suggestions. Guess I'll have a few more USB 3.0 sticks lying around for whatever.