Fear not, you still can get it to work
1st, you said you got a 256mb jasper... so you should have used nandpro lpt: -r64 nand.bin
You said you dumped it as 16mb.. still fine. Let's fix it..
nandpro lpt: -r64 nand.bin - run this command twice and compare the files.
when it match, run this command
nandpro nand.bin: -w16 nand.bin 16mbnandimagename.bin (where 16mbnandimage.bin is how you called your 1st 16mb nand dump)
With that, you should have your original filesystem back.
Rename nand.bin to stock.bin
Wire your jtag, regular way, not the fancy pants aud_clamp way.
Write xellous to your console using this command: nandpro lpt: -w16 xellous.bin 0 50
When it's done, read it back with nandpro lpt: -r16 verify.bin 0 50
Compare verify.bin against xellous.bin. If it matches... you're good to go
Take your lpt cable out of your pc, take the power supply from the back of the console.
Plug your dvd drive in and plug back your power supply
Power the console and you should get xellous. Remember Xellous only output images to vga or component.
Write down your cpu key.
Now download this script - www.tinyurl.com/fb4script.com
and read the included txt file.
Feed it your stock.bin nand image, your cpu key
Follow the prompts and make sure to answer NO to the aud_clamp question.
When it's done, copy updflash.bin to a pendrive and use that pendrive to flash your console.
When it's done, remove psu from the back of the console, remove the pendrive, wait 30 seconds and put back your psu.
Power on the console. You should boot to the dashboard.
It worked? Cool.
Now it's up to you to choose to aud_clamp it or not.
If you choose to aud_clamp it, feed stock.bin to the script again.. and answer yes to the aud_clamp question.
Then flash it again using the pendrive and shut down the console.
Now modify your wiring to reflect aud_clamp requirements.
Assemble your console again.. and it should boot fine.