Kloe,
Spinning. You do it on the JAR FI course and the 140 is probably better than the 172 asr Cessna did a very good job with the 172 as you can recover from all but the most aggressive wing drop stalls and stable developed spins with aileron thereby destroying all your learning points.
A more important point is what ever the platform you do want to be comfortable with spinning so you can approach "abeit incipent spin recovery" with your student in a calm and confident manner.
Career Instructor. Depends on your financial requirements. The job is superb or awful depending on whether you like instructing. Your training environment (aka school) will also be very important. I instruct as a second career and find it immensly rewarding but I am buffered by a pension.
Potentially there is a career as a professional FI as all the other FIs move on to larger ac so you must (assuming some skills (aviation & people)) have a serious chance of becoming a CFI... and therefore someone Gordan will welcome as a 40% tax payer
Good luck