Well, you do not want Trisquel on the external drive, right? It is possible
but I do not really know how (in particular how to get Windows to boot when
the external drive is not plugged in) and it would be slower.
So, if I were you I would use GParted to "delete" /dev/sdj3 (the root
partition, where the Trisquel system is), /dev/sdj4 (the swap, an extension
of the RAM if it becomes full, or to hibernate) and /dev/sdj5 (where the user
files would be) and then "resize" /dev/sdj2 to take over the whole free space
(as it used to).
See if my analysis in the previous post is correct, looking at the files on
the different partitions.
If I am right about /dev/sda2 containing data and not an operating system,
then try to take the "boot" flag off /dev/sda2 and see if Windows properly
boots.
If it does, we can then proceed to installing Trisquel on an internal hard
drive (/dev/sdc?).