A) done right yes
B)any solder should work
C)20watts? you might want more heat
D)Yes and no
E)clean the wire with about 150 grit sandpaper, also what I do, is take a small drill bit on a drill motor and insert it into the coupler, moving it in and out as to scratch up the inside of the coupler, exposing the freash metal, the same way you're exposing the freash metal by sanding the wire. Then Very important!! push some Flux into the coupler and dip the wire in the flux also, If you don't use flux the Solder will not Wick into the coupler. When you get the coupler/wire hot enough you'll see the solder being wicked in or pulled it to the coupler. once it stops wicking in you're done. this is the same way your houses copper pipes are put to gether, Done right it won't come loose
F) Let cool and with the wire in a vise and holding the coupler with pliers you shouldn't be able to pull it apart, if you can? go back to "E" and start over

This will take a little practice to get good at.