I'm really sorry to hear that you have had bad experiences with SJ, knowing some of the crew that work there they seem to be a really professional organisation. Maybe its down to being a new company who are still finding their feet?
I've worked for quite a few airlines now and my experience is that on offering you an interview they will try and accomodate you as best as possible but as with any job interview, yes there are times that the interview time or date clashes with your now job. Its just unfortunate. I don't know many jobs that you would go for that could offer you an interview for example at a weekend or in the evening.
Don't let all this cloud your judgement. If you really want to fly, i can honestly say that they seem like a great outfit. Be patient and keep trying.