Yeah, most of your assumptions aren't miles off.
If you do the FI course at ACS there's a very good chance they will give you a job. No idea if the same is true at Tayside, it wasn't for a while but that was mostly because their existing FIs were not moving on. There is a person there who seems to be using the words "virtually guaranteed" a job with Loganair, as has been said before, this is without question "complete sales bull" You will be guaranteed an interview IF you get a job at Tayside but that's it and you need to make sure you don't piss anyone off while you're getting there as well
. Logan also do look at people from a wide variety of backgrounds so if you definitely want to work for them, don't worry too much.
No idea who does the FI training at Tayside these days, it used to be good but the entire training team have changed since I was there. I have trained and worked with the guys at ACS and they are excellent, particularly the FI course, if I was to choose between the two it would be ACS without question.
Ask yourself if you really want to teach though, without being fully motivated to do it you could end up spending money on something you don't like and that has a negative effect on the students.
Doubt training in one specific place will be any more likely to get you a job as an FI, you need to be in the right place at the right time and that means lots of footwork. There's a great PPL school at ABZ as well, you may want to talk to someone over there.
If it was me, doing it all over again, not in Scotland. I would choose the school I was going to do my IR at and do the CPL there, then go do the FI at one of the specialist places, Pooley's or On Track. Airlines want to see you do the ME-IR and CPL at the same place, they don't seem to care where you do your FI
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Good luck with the ATPLs
they are such a pain in the nuts.