You are probably asking a biased community
From personal experience (I run a software company) I'd say software testing is generally a dead end (coding wise), unless you want to stay in that area writing test scripts.
It's really important that you find out what types of industries you have locally and what type of language is prevalent there. Each language has it's own nuances that can take many years to master so you are best to go straight for the language that you want to learn and will get the most out of. Employers will look for keen people with some experience in the requisite languages. There are many junior developers out there so anything that puts you in a better position is worth doing.
As for anything Amiga related: only do this if it is in line with your goal. Working on a 'dead' OS will be viewed by many as a pointless exercise (and a distraction for your potential job). By all means do it as a hobby, just not as a means to make yourself stand out. You'll have to invest a lot of time to learn Morph OS as you suspected.
Finally, read books, learn the terminology and best practices and experiment with them and you'll get on your way. If you struggle to get interviews you should get some college courses on your CV and make the most of their careers advisers who will be able to put you in touch with employers.